Another Sportster's (finally) on the road!
 

The Sportster has her plates so I took her out for the first drive this afternoon.

https://farm1.staticflickr.com/650/2...a00da2d0_b.jpg
https://farm1.staticflickr.com/570/2...53dc117f_b.jpg

I only went a few miles for the first trip just to get a feel for it. It seems to be pulling well but I need to sort a few problems out, the main one being a significant vibration at 50+. I had the front wheels balanced this morning ahead of the drive as I'd knocked all the weights off when I had my steering rack issues. The vibration is coming through the body rather than just the steering so next stop is the rears. I know that there's a very minor buckle in one of the rear wheels but shouldn't be enough to create so much vibration but it will be my first port of call. I'm just hoping it's not an issue with either the prop-shaft balance or angle between the gear box and diff.

I still have the suspension set up for the IVA test so I've got quite a bit of toe out plus the tyres are pumped right up and the suspension is all on the softest settings so addressing these things may help a bit. I've also got the new 40mm spacers on the rear so I'll see if I can run it without just to eliminate them from the equation.

My front cycle wings still bounce around quite a bit even with the extra reinforcement I fitted but I can see a fix for that already. Generally the car seems very squeaky/rattly but as I've never owned a car like this, it may just be noises I never normally hear cocooned in the cabin (I get obsessed with finding even the tiniest squeak in my cars).

I think the length of the nose is going to take some getting used to too. I was a bit paranoid about clipping the curb as you have to lean your head around to see where the wheel is. That will become second nature after a short time though.

If anyone's got some good advice on suspension settings for the road, I'd be interested. I'm going to change to a spot of toe in on the front and generally lift the ride height all round to make it a bit more speed bump friendly. It's the amount of damping front and rear I'm not too sure on from the point of view of the bias.

Dear Ian,
firstly, a big congratulations on finishing your car and getting it registered! :smile: I bet your first drive was exciting and that view down the bonnet is something to savour!!
I think you'll get used to the front mudguards bouncing around which, so long as they don't fall off, is quite normal and nothing to worry about.
From memory I used to run with tyre pressures around 18-20 psi and only a couple of clicks from full softness on the front shocks.
I'm not sure about the vibration but perhaps you've flat spotted your tyres on your first lap (...well that's what they always say on F1 TV :lol:)

At least we finally know that gearbox works okay :madgrin:

Happy motoring.............peter.

hey that's a thought, maybe it's the gearbox causing the vibration :)
No, it works fine and changes are nice and smooth, well, provided I press the clutch down properly. It takes a strong left leg with the current setting.

I've basically worked out where the mid point of rebound setting is on both front and rear dampers and set to that now. I'm going to get a full day of testing in tomorrow so should be able to play around with things a bit.

One thing I did notice when I had the car jacked up is the front NS wheel has a slight buckle. I thought I'd put the dodgy one at the back deliberately as you'll notice it less there but now I'm wondering. Hopefully that's all it is and I've found the problem rather than I now have 2 buckled wheels :(

The other things I noticed on my test drive were that the oil temp never got really warm on the whole 6 mile round trip, maybe 50 degs. This may be because there's so much air flow round the sump or that 6 miles just isn't long enough.

I've also noticed that oil pressure isn't really getting very high on my gauge and the light blinks now and again. The oil level is good but I did add some of that tappet loosening stuff (can't remember the name) a year back when I had the VANOS rattle issues. The oil seems more like the consistency of veg oil than engine oil so I wonder if it's a bit thin. A change wouldn't hurt I think.

Well done :)

Can you try the wheels from your daily driver on there see if tht cuts out the vibration? That is if the tyres on the rear ones will fit in the arches as the MV type 1's are staggered!

If sorting the buckled wheels doesn't cure the problem I would suspect the prop shaft! Has it been apart or new parts been fitted? I once replaced just the front yoke on a Mk2 Cortina (splines semed a bit worn) but didn't have it re-balanced. At 50 mph the vibrtion was horrendous! Ended up refitting the old yoke which luckily I had identified and all was well again.

Also do a quick check that there aren't any dribbles of paint or underseal on the propshaft as that will be enough to throw it out of balance (as does repainting it!). Peter.

The prop was a new custom made unit and had been balanced (had a little plate welded on). That doesn't mean it was correctly balanced mind you. I'm going to rule out all the more common causes first as that will be a pain to get looked at. I refurbished the drive shafts too so it's entirely possible they're out of balance though being so thin I would have thought it unlikely to cause a problem at road speeds.

I reset the toe in on the front this morning then gave my wheels an inspection for buckles. The one I knew about was on the back after all so that has to be addressed anyway. what I thought was a buckle on the front I now think is just a bit of corrosion damage on the bead which after they we're refurb'd shows as a minor inward dip as you spin the wheel. It isn't actually out of round.

I popped down kwikfit with my good spare wheel/worn tyre and my buckled wheel/good tyre to get them swapped over and they refused to do it. Said it's against company policy as they can't guarantee the work unless the tyre is brand new. Sounds to me more like they're only interested in helping if there's a tyre sale in it for them. Nowhere else is open today so I'll go to a local garage tomorrow and get them to do it. I can't just get a new tyre put on the good wheel as you can no longer buy the one I need to match the other side of the axle. It's pretty frustrating as it writes off an entire day of good weather and testing. I could probably fit my MV-1 front 225 wheels on the back of the Marlin but Patrick is right, they are a staggered set up with 255s on the back. A bit wide for the Marlin.

I've fixed up the front wings a bit too. I think the main problem is the weight of the GRP. Has anyone fitted Carbon fibre wings?

I've been doing a bit of reading around propshaft vibrations and come to the conclusion that the M5X engine set up in the sportster really isn't going to help.
Take a look at this link

http://www.therangerstation.com/tech...onangles.shtml

There's a diagram about halfway down showing the correct way to install a propshaft in terms of angles between the gearbox and diff. The Sportster set up is the worst possible. The diff is true to the chassis but the engine/gearbox is at an angle meaning that at best you'll have and angle at one end but not at the other. In the worst case (which is what I think we have) there is an angle at both ends but most importantly they don't cancel each other out and the angles are different so by the time the rotation gets to the diff, it'll be accelerating and decelerating all over the place causing a massive vibration. This is just looking at the layout from above before you even take into account any difference in height or angle between the gearbox and diff.

I'm now determined to get the engine sitting straight even though we've been told before the car is designed this way. That's moved to the top of my winter projects list.

That's an interesting link and worth following up BUT what do other Sportster owners think? Have they had similar issues? If not IMHO it has to be a simple fix unique to your car rather than an inherent design issue. I remember a tyre fitting chap, years ago, saying that wheel(s) out of balance always seemed to cause vibration at either 30mph or 50 mph, but no reason was forthcoming! Peter.

I have never had any vibration issues. My wheels were new and the propshaft was custom made (dave mac).

Bearing in mind that the propshaft rotates at 3x the wheel speed - I would have expected a highish frequency vibration if that was theculprit. (Perhaps it is - you dont mention details...)

Wheel vibration should be quite rcognisable - I guess most of us have had that at one time or another.

How good a fit was the propshaft? On my car (E30 based) I had to reem out the centre hole so it was a good fit over the gearbox spigot. The spigot is used for centralisation on the E30 box.

Cheers Robin

I wonder if putting the car up on four axle stands and then 'driving' the car with and without the rear wheels would shed any light on the cause. (but do make sure it cannot drop off the stands!!)
I'm guessing that if it is propshaft induced it will still vibrate without the rear wheels fitted.

I know I joked about flat spotting your tyres but maybe if the car has been sitting on the old tyres for a long time then maybe they have deformed?

My bet is on your old wheels or tyres...........

Hi Ian,

Great news and many congratulation in getting the car legal. Lets hope we get a few more good days before the weather starts to really go down hill.

I had a prop shaft made for mine and I put a new set of wheels on the car and the set up, with the engine and gear box at an angle must be much the same as yours. I've had no vibration problems at all (just bought up 11,000 miles this weekend) so I wouldn't focus too much on getting the engine straight. I think I would be inclined to focus on the wheels first and if you could change them all out, or at least fronts and then rears its probably the first port of call, at least to eliminate them if nothing else.

Cheers

Nigel

Yeah, I'm not going to dive straight in and start moving the engine around (there are too many things tightly fitted around it) but just feel that I should have followed my gut instinct back at the start of the build and made the engine fit in straight so this kind of thing wouldn't be on the cards. I'm planning an engine swap/stroker rebuild so that will be the time to make these kinds of alterations.

It wouldn't be the first time (by a long shot) that I've over thought a problem and won't be the last.

I know most vibration issues come down to wheel balance and then can be exacerbated by suspension play or worn bearings (both of which are new all round). Vibration always comes down to a rotating component in the end and as the wheels have the largest radius, they're the obvious first choice culprit. The suspect wheel is in the boot of my car ready to get it looked at tomorrow and hopefully that will sort it out.

I've spent a fortune over the years chasing down vibration issues on cars and it's always been balance or not putting my hand deep enough in my pocket when buying tyres in the first place. I never buy anything but premium tyres these days as you end up wasting money on inferior products and subsequent trouble shooting otherwise.

I did think about putting the car up on stands and running it at about 2500rpm in 5th which would be roughly the speed the issue occurs at. I'm always slightly scared of that though but it will be my next port of call if the wheels don't solve the problem.

If you put it up on stands also put some wheels under it, they give a nice big surface area if theres an issue with the axle stands :)

Looks like bad news for the moment.

I've just run the car with the back end on stands and with the rear wheels on or off, you get the bad vibration at around 40mph.

I left it running on idle in 5th and from what I can see of the prop past the exhaust, it didn't look that smooth. Maybe some run out around the slip joint area.

the good news is that the drive shafts didn't visually seem to be vibrating so the problem must be between the engine and the diff. There's a little vibration when rev-ing the engine through 1000-2000rpm but nothing to get worried about. It certainly doesn't cause the issue when reving through the range in neutral which I guess rules the flywheel and clutch out too. So I guess it can only be the gearbox, prop or diff. The former will be easy to rule out if I disconnect the front end of the prop though I'm pretty sure I tried that when I first got the engine running but before installing the prop and I would remember a vibration like this. I don't remember any vibration from the diff on my drive home after buying the donor either.

Tomorrow I'll get it a bit higher in the air so I can look underneath properly, maybe drop the exhaust and try and film it at the resonant point to see what's going on. I'm hoping it is something silly (but not funny) like a bolt working loose though I can't quite see how that would have happened so soon.

If the prop does look dodgy I guess it's easy enough to send it off and get it looked at.

U/Js
 

Have you checked the alignment of the Universal joints in your prop shaft?
If they are not matched to the exact spline you will get vibration - particularly since the input/output flages are not in the same plane.

Hi Mike,

I've not checked the UJ alignment directly but I did look at some photos prior to fitting to see if this might be the issue. It certainly looks ok here

https://farm8.staticflickr.com/7313/...5541c3f4_o.jpg

I think some filming running though the gears will help, hopefully I can get that done tomorrow evening. I think a check of all the bolts is also a logical next step.

Have you found the cause ?

Not just tight but are the bolts and nuts all identical? i.e. same length. Also as someone said earlier check that the flange inner shoulder and recess is a good snug fit and doing the centralising of the mating parts and not just relying on the bolt holes. Peter.

I'm still looking into it. So far I've tested the following:
- rear wheels off
- spacers off
- discs off

The problem persists. When I had my first IVA test and the examiner ran the car up to 70 there did not appear to be any vibration visible, audible and he didn't mention feeling it (I would have as it's not bearable). That got me thinking about what had changed and I realised I had swapped the rear brakes over from my E46 since that point but at the second IVA, we only hit 25-30 round the yard. I was hoping that it was something to do with the brake swap. Unfortunately this turn out not to be the cause as even with the discs off, it still shakes.

Unbolting the drive shafts from the diff and then unbolting the prop from the gearbox output are next. The bolts are all tight and the same length. I did have to modify the heads on some but tested they were all within a gram before installing. The flanges do appear to be mated properly both ends and the UJs are aligned. The welded on weights on the prop are still intact and there's no evidence of physical contact with anything. I'm also suspicious of my gearbox mount but would think that would cause a clonk on acceleration or coming of the throttle quickly rather than a shaking.

I've found a test to rule out the flywheel or clutch so will try that too.

I'm a little worried that I've ruled out the engine too soon because it doesn't vibrate when just rev-ing freely. Could worn crank thrust bearings be a factor? Would rev-ing in neutral but with the clutch engaged rule that out? I'm thinking of the force down the crank when under load.

Ditto.
I would remove and clean the mating surfaces both ends to make sure there is no paint trapped. I'd also check how snug the fit is of the rear centralising raised section which locates in the diff flange.

yep, I'm going to check the fit of the shaft both at the diff end and the spigot on the gearbox. I do seem to remember having to open out the hole in the gearbox end so it would fit like Robin said, but that it was still a pretty snug fit. The front was custom made to my P.C.D specs where as I think the rear was an off the shelf part for a BMW. I also had to open up the bolt holes on the diff end of the shaft to 11mm as the P.C.D wasn't quite perfect but as the locating ring was ok, didn't think it would make any difference. Maybe I screwed it up.

I have the day off tomorrow so can get stuck in without having to fight the dark and the unsociable aspects of rev-ing a car at 8-9 in the evening.

I think I may have tracked down at least part of the problem. I carried on disconnecting the drive shafts today and the problem was still there so I bit the bullet, dropped the exhaust and then the prop. With the prop shaft out, the car runs perfectly smooth up past 60 in 5th with no issues which confirms that the flywheel, clutch and gearbox aren't part of the equation. Here's a pic of what I found when I inspected the prop.

https://farm1.staticflickr.com/647/2...42a789d1_b.jpg

The diff end flange on the prop has a raised section which mates with a recess on the diff input flange to ensure it is centralised. As you can see, there is yellow paint stuck tight on the flange now which is the torque paint from the diff input pinion nut. This means the flange must have been tight against the input shaft end and it's therefore likely that the prop wasn't seated properly even though the bolts were done up tight. It may even have been affecting the pre-load on the pinon nut though I suspect it would take a bit more than that.

I'm going to send the prop back to the manufacturer and get a recess cut in the end and also get him to recheck the balance, run out, misalignment and generally reconfirm the measurements from my drawings.

I now have the fun of putting all the other disconnected parts back on the car. Having the car up in the air while I'm waiting will give me chance to improve a few things I'd put off until after the IVA such as the gearbox and exhaust mounts.

Looks like you are homing in on the problem. I'm not familiar with BMW parts but that location spigot step is much lower that I have seen on other cars. Worth putting a vernier across it and comparing with the mating recess? As there is so little to locate on it may not be very effective in centralising the flange. Peter.

Hi Pete,

It's exactly 2mm high but I've a drawing bailey-morris supplied for the same part way back when I was first getting quotes and that says 3mm max. You can see the diff input flange below. There is a very shallow recess to fit into and in this instance, I can see that I need to spend some time cleaning the surface up a bit too as there's a small amount of rust left in there. I really could do with getting the face of the diff flange machined too as you can see some corrosion top and bottom where it wasn't covered by the original BMW UJ.

https://farm1.staticflickr.com/681/2...1c56bc89_b.jpg

Interesting. I wouldn't do any machining on the flange as you would have to reset all the diff preload as you would have to remove it to do the job. I would do some very thorough hand scraping to just remove all the rust scale and then a smear of waxoyl to inhibit further corrosion. If you have an old flat file and grind the teeth off and then put a slight radius on the end it will do a good job of the scraping.

Just a thought. Was your special flange fitted before the prop was balanced? It should have been. Did you remove the flange to enlarge the holes and if so did it go back on the yoke in exactly the same position or was it replaced 180 degrees from original? Peter.

Yeah, it's the pre-load issue that puts me off removing the input flange. I was thinking that some careful swipes with a fine file avoiding the un-corroded areas would be the best approach.

As far aware, the prop was balanced with both flanges fitted. When I opened the holes out 10mm to 11mm, I did it with everything still attached, I've never actually separated the slip joint as there's never been the need.

It's in the post so I just have to wait and see now.

Best avoid files as they cause raised areas at the edges of the cuts. An engineers scraper (made cheaply as above) is the preferred method and you will be surprised how well you can locally remove metal (or rust flakes) without disturbing the surrounding metal. Secure the flange in a vice and use both hands, one to do the pushing bit but the other to control where you are workig. Peter.

Good advice Pete. I actually found a broad gasket scraper amongst my tools and that did the job nicely.

https://farm6.staticflickr.com/5772/...edd13ce1_b.jpg

I used a screw driver to scrape the corrosion out of the recess and then blocked the face of the flange with some wet and dry. I also ran a small wire brush wheel around the inside of the recess with a dremel to ensure there was no crud left in there to spoil the fit.

It's now lovely and smooth with very little corrosion left (as you can tell by the brightness of the flash reflection). I've smeared a little copper grease over it now just to keep it that way.

Good result eh! Will be interested to hear the results of the checks on the propshaft when you get it back. Peter.

Any news yet about the propshaft? Peter.

Best not to get me started. Having posted the prop back to Autoprop UK on Saturday morning, Parcel Force have been incapable of finding the address until 5pm today despite 4 calls in the evening over the week to explain how to get to a location that is clearly visible, with a sign from the main road. I can see it nearly 200 miles away using google street view so they must be pretty incompetent as I could find my way there with nothing more than an AA road atlas if not memorising the route.

I'm pretty sure the £17 it cost me was for a ParcelForce48 service, not ParcelForce152.

I'll let you know once Autoprop have come back to me. It should be a pretty simple job to take the yoke off, machine the back and re-assemble.
cheers
Ian

How completely frustrating for you. Why is it that the more automated and computerised things become, the people that use them seem to lose all sense of direction, location initiative and common sense! Ah well soap box put away now! Hope the wait for the prop is worth it in the end. Peter.

Hi Ian. Any news back from Autoprop? Peter.

Hi Pete,

I spoke to Mike down at Autoprop on Tuesday to make sure he understood the problem but he hasn't got back to me yet. I'm going to chase tomorrow as the days are getting colder, nights drawing in and I want to get some shake down time on the car before the winter. Hopefully he'll have good news for me.

Hi Ian. Fingers crossed then. I will be really interested to hear what caused the vibration when it is finally resolved. Peter.

Hi Ian. Any news from Autoprop? Peter.

hi pete, my prop should be winging its way back to me at the moment. hopefully I'll have it by the weekend, get time to fit it and report back.

Hi Ian. That's good to hear. Did Autoprop offer any comments about the possible cause of the vibration or what they have done to fix it? Peter.

My prop is back

https://farm1.staticflickr.com/634/2...fd0c6f2b_b.jpg

They've not done quite what I asked for which was to cut a recess a certain size concentric to the the locating part but this dish shape should still work just as well. It's the same principle used on the BMW part (pic courtesy of peterux)

https://farm1.staticflickr.com/657/2...9257c687_b.jpg

I noticed that the balance weights originally welded on are now missing but there's fresh paint, so maybe it was incorrectly balanced from the start too? Or maybe it's now going to locate properly but be out of balance:icon_confused:

No time to fit it tonight but should know if my problem's solved by Saturday

Let's hope this one is good!
Looks to me like that is a completely different flange so hopefully they have rebalanced the whole shaft. The 'scooped out' cavity looks good but the raised locating spigot looks a bit shallow?
And I can't understand what could have caused those tangential scratches? As a custom propshaft builder I'm a bit surprised they don't have a standard BMW diff flange.

Hope you enjoy the next test drive :madgrin: