Wheel & Tyre options - Page 2

Paul D · #21 15th January 2012, 16:35

Cheers guy's, what a fantastic response in just a few hours. This is a brilliant resource for all of us builders.

I am a bit nervous about drilling the rack, so will play conservative and fit the biggest tyres that won't foul the chassis on my 15" wires.

To sum up so far using the excellent tyre size calculator program:

The original wheels were 155/80/13 with overall diameter 57.82 cm - ok.

Davecymru has fitted 165/65/15 with overall diameter 59.55 cm - ok.

JW52 has fitted 185/55/15 with overall diameter 58.45 cm - ok.

I have fitted 185/70/15 with overall diameter 64.00 cm - PROBLEM!!!

So the magic overall diameter lies somewhere between 59.55 and 64.00 cm.

Could I ask JW52 how many mm clearance you have between the tread and the chassis rail when they are at their closest point of the steering lock?

Does anybody else have a wheel tyre combination that adds up on the tyre size program to give an overall diameter greater than 59.55mm -AND STILL CLEARS THE CHASSIS ? Don't worry about the bulkhead, we can all fix that.

Thanks again, this must help others out there to avoid costly mistakes buying the wrong size tyres.

Paul D.

lancelot link · #22 15th January 2012, 17:01

pretty sure the 66 car had 165/75 x 15 which equates to 62.85cm and they touched ...just

Paul D · #23 15th January 2012, 18:35

Thanks Gary, if 165/75/15's just touched the chassis at 62.85 cm, then the remaining unknown possibles in ascending size look like:

185/60/15 - overall diameter - 60.30 cm.

175/65/15 - overall diameter - 60.85 cm.

165/70/15 - overall diameter - 61.20 cm.

185/65/15 - overall diameter - 62.15 cm.

I think the last is probably too close to Gary's 62.85 cm which is known to touch to risk trying.

Anybody else out there tried any of these on their car with 15" rims? It would be great to hear your experiences.

Cheers, Paul D.

Mister Towed · #24 15th January 2012, 18:38

I've bolted up my 165/80/14's (61.96cm) on the front and reported back that they cleared ok with a few mm to spare.

That was after putting it on full lock one way, finding they cleared then assuming it would be the same both sides. Now I've tried full lock the other way I've found that the nearside wheel just fouls the chassis rail. This is probably down to the different wear on the old tyres and I've yet to try them with the bulkhead fitted, which is still a work in progress...

Now, my old tyres are worn smooth across most of their surface which probably knocks about 10 -15mm off the original diameter of 61.96cm. So, they're actually about 60.5 to 61cm.

Based on that assumption I'm probably going to fit 175/70/14's giving 60.06cm and hopefully no fouling issues. If Trevor's car was anything to go by they'll still look pretty good. He used 165/70/14's (58.66cm) and got the stance I'm looking for.

http://sammiospyder.blogspot.com/

Given your 5.5 x 15's I'd be looking at 175/65/15 (60.85cm) or 185/60/15 (60.3cm) for the best combination of looks vs clearance.

It's also worth bearing in mind Phil Jacklin's BRG car which is running 185/70/13's (58.9cm) and which looks mighty fine imho.

When it comes down to it, how much difference is another 20mm or so on the sidewall going to make to the looks of the car?

To be honest, it's only ever going to get noticed by us Sammio nerds anyway.

Paul D · #25 15th January 2012, 19:46

Thanks Mr Towed, great information. Just what I was looking for!

Having Googled 'new car tyre tread depth', it looks like for a normal road car the consensus is 8mm. So if yours are actually fully smooth, we can take 16mm off the original diameter of 61.96 cm. This seems to suggest that 60.36 cm. will just touch, if only because of the odd distortions in the chassis over time.

Looks like your proposed 175/70/14's at 60.06 cm. would be a perfect size.

For the 15" wheels, the safe choices seem to be coming out at:

175/60/15 - overall diameter - 59.10 cm.

165/65/15 - overall diameter - 59.55 cm.

185/60/15 - overall diameter - 60.30 cm.

As Mr. Towed has suggested the 175/65/15 at overall diameter of 60.85 cm. could well be a good fit, but the numbers suggest that with full new treads might possibly just touch on full lock.

Any more contributions to the discussion out there please? Its good to share !!

Paul D.

Mister Towed · #26 15th January 2012, 22:05

If you look closely at my current front tyres you'll se they're down to the chords on the insides but there's still a bit of tread showing on the outside edges, which is where the nearside one fouls.

It does look like 60 to 61cm is the limit without too many bulkhead mods and 62cm with some subtle hammering of the footwells is possible. Once you go to 63 to 64cm fouling on full lock seems to become an issue.

The only reason you'd go that big though is if you simply must have the genuine 50's stance that '66 had rather than the slammed look that Trevor (and quite a few others) have achieved on theirs.

Mister Towed · #27 16th January 2012, 16:56

I trial fitted my bulkhead today (which I'm still in the process of repairing), refitted the steering column and put it on full lock. The 165/80/14 fouled the bulkhead, pushing it back about 10mm. Looking at where it touches - the crease line roughly half way up, this is mostly down to my having lowered the front springs by almost four inches.

I then swapped one of the front wheels for one fitted with a 155/80/14" tyre and tried again.

Although the pictures probably don't look much different the 155 tyre just clears the bulkhead with about 1mm to spare.

The difference between the physical size of the 155 and 165 tyres is quite surprising when you put them together, although the difference when seen in isolation and fitted to the car is less noticeable (the 155 is the middle picture).

Given the results I'd say that you can probably fit a 62cm diameter tyre, 185/65/15 for example, without modifying the bulkheads so long as you don't lower the front as much as I have, while 60.5cm is pretty much the limit on mine. So it's 175/70/14's for me.

tlrtone · #28 16th January 2012, 19:16

great bit of research Mr Towed!

lancelot link · #29 17th January 2012, 18:56

Yes thank you....

This stuff is priceless to a new builder and would take me all my time to research / calculate......

I am so pleased with the success of this forum on so many levels ....we have had customers order a kit who have said the friendliness and helpfulness of this forum has been a factor in making their decision...starting a new project , on whatever level and with whatever degree of ability can be a daunting thing and the amount of info and data on here in a fairly short period of time has been immense...

Nick59 · #30 17th January 2012, 20:55

All this has made me look at what was fitted to my wheels when I bought them...I have 48 spoke 15inch TR2 wheels and they are fitted with 155 SR 15 tyres....I quite like the look of them so probably need to check clearance.

Mister Towed · #31 17th January 2012, 21:27

Quote:

Originally Posted by Nick59

All this has made me look at what was fitted to my wheels when I bought them...I have 48 spoke 15inch TR2 wheels and they are fitted with 155 SR 15 tyres....I quite like the look of them so probably need to check clearance.

At 62.9cm they'll possibly need a bit of bulkhead bashing to fit. Let us know once you've bolted them up.

Paul D · #32 21st January 2012, 16:58

Had a word with our friendly local garage proprietor this morning, and borrowed a brand new 185/60/15 to try. They kindly swapped it and the inner tube onto my chrome 15" wheel for me to test out on the car.

The bad news is it still fouls on the chassis rail, but at a point much closer to full lock, approx one quarter turn of the steering wheel from the end of travel.

I must admit I am having doubts about the measurements since it comes out on the on-line calculator as 60.3 cm total , but I can only make it about 58.5 cm in the flesh as it were. I wonder if I am worrying too much about hitting the chassis on full lock - does anybody know if this would be an Mot failure point?

Will try and post some pic's later.

Paul.

Paul D · #33 21st January 2012, 19:07

Ok here goes..

So here's the tyre on the wheel touching the chassis.

And here is a comparison between 185/60/15 and the old 185/70/15.

The new tyre has about 8mm tread and my old ones have about 6mm.

I think part of the problem might be the width of the tread, I have a feeling 165's might be less of an issue & might try 165/65/15's next.

Perhaps I should mention that my springs are standard at the moment, and the engine is still in the car. It will need lowering at the front, but this is unlikely to significantly affect the chassis fouling issue as far as I can see.

Any thoughts out there?

Paul D.

froggyman · #34 21st January 2012, 22:20

Hi, most testers will fail the car if the tyre fouls on the chassis or body as stated in the testers manual. During driving and braking the tyre will flex and to a certain degree the bushes in the suspension wishbones etc. will give a little thus any clearance to be reduced. I think the only positive way to overcome this is to move the chassis rail back slightly. I don't think this would be questioned when the car is inspected for changes to registration document as no measurements are taken. They are only interested in the fact that the chassis is complete and after all,welding repairs and outrigger replacement is allowed. This is the route I will take I think when I progress from a lurker to a builder. The bulkhead can then be freely modified as necessary to suit. This surely is better than the big hammer approach and allows you to use the wheel and tyre setup of your choice.

Paul D · #35 22nd January 2012, 08:03

Thanks Froggyman,

Makes perfect sense that it would be an MOT fail, good to have this confirmed though. I do hear & understand your view on moving the chassis rail, however for myself I would prefer a 'bolt - on' solution at this stage to speed up getting this project on the road. Maybe next time!

So far...

Original wheels 155/80/13 with o/d of 57.82 cm - ok.

JW52 has fitted 185/55/15 with o/d of 58.45 cm - ok with small bulkhead mods.

Trevor has fitted 165/70/14 with o/d of 58.66 cm - ok not sure of mods?

Davecymru has fitted 165/65/15 with o/d of 59.55 cm - ok with some bulkhead mods.

I have trial fitted 185/60/15 with o/d of 60.30 cm - PROBLEM fouls on chassis.

Mr Towed has trial fitted 165/80/14 with o/d of 61.96 cm - PROBLEM fouls on chassis

I have fitted trial 185/70/15 with o/d of 64.0 cm - PROBLEM fouls on chassis.

I guess the choices are getting a little clearer. has anybody else tried any other combinations that fit o.k.?

TheGiantTribble · #36 22nd January 2012, 09:16

Now I might be talking a load of B$%*&s here but...
The problem looks from the photos like it's only a problem close to full lock, and I see people have try'd reducing the available lock.
Wouldn't it be easier to use a different stearing rack, ok might have to giggle a bit due to different sized track, mounting points but doable I would have thought. And less prone to MOT man going 'ere your chassis a bit bent' after people have used a Irish screwdriver to adapt the chassis.
I'll shut up now :-)

Mister Towed · #37 22nd January 2012, 09:36

Quote:

Originally Posted by Paul D

I must admit I am having doubts about the measurements since it comes out on the on-line calculator as 60.3 cm total , but I can only make it about 58.5 cm in the flesh as it were. Paul.

I'd also wondered about the accuracy of the tyre size calculator as I found it difficult to physically measure the height of the wheels without access to a jumbo vernier caliper.

As luck would have it, before I found http://www.kouki.co.uk/utilities/vis...ize-calculator I used to work out the tyre size the old fashioned way, so for your 185/65/15 the calculation would be as follows:

A/ Convert wheel size to mm -
15x25.4 = 381

B/ Multiply tyre width by aspect ratio then multiply by two (for top and bottom sidewalls -
(185x0.6)x2 = 222

Add A and B together -
381+222 = 603mm or 60.3cm, which is what the calculator says.

Both methods assume that the tyre is exactly 185mm wide and that the sidewall height is exactly 60% of the width. There is a danger, however, that those dimensions are nominal and substantial variations due to manufacturing tolerances is the norm.

One thing we haven't considered yet is the effect the width has on clearance. The original setup used 155mm wide tyres and we're all increasing this by between 10mm and 30mm.

You wouldn't expect this alone to make much difference but most of us are also increasing the track width by adding splined adaptors. This has the same effect on the front suspension geometry as fitting something like a 7" to 8" wide wheel, meaning the outside edge of the wheel scribes a much larger arc as the steering is turned. Sadly, the wider the arc the more likely the tyre is to foul on the chassis and/or bulkhead.

If you take a look at this picture of my MGB wires fitted to my chassis you'll see that the discs have ended up completely inboard of the wheels. With the Vitesse wheels fitted the discs are fully enclosed inside the wheels, so, although the tyres on the wires (poetry!) are only 10mm wider than standard, they scribe a considerably wider arc.

I hope all that makes sense and good luck finding a tyre size that works for you.

Oh, and I really like what you've done with the flexible conduit zip-tied to your frame to protect the loom. I'll be pinching that idea, thank you...

davecymru · #38 22nd January 2012, 10:29

Have we also considered any differences in Chassis between the different Herald models, and also between the different Vitesse models?

I've heard some comment that they're all identical, but then again i've also heard comment that there are some slight differences between the 1200, 12/50 and 13/60 ? It's just something to add to the confusion

Patton · #39 22nd January 2012, 18:40

There's difference's between all of them none are to precise in manufacture or to square and thats on the same model almost a case "that's near enough"

Mister Towed · #40 23rd January 2012, 08:01

Quote:

Originally Posted by Patton

There's difference's between all of them none are to precise in manufacture or to square and thats on the same model almost a case "that's near enough"

I must agree Patton. My front wishbones appear to be mounted at slightly different points on the chassis as one side has more clearance issues than the other. There's no sign of crash damage and I've checked the chassis rail orientation and it's all true. The only possible answer is that there's a few mm difference in the way they were bolted/welded up side to side.