Will A 9" Rim Fit???

Jon@JNRacing.co.uk · #1 20th July 2007, 08:41

Well, the answer to the above question is YES

.

After spend months in the cold garage taking measurements and working out if we could fit a 9J rim, our wheels turned up the other day from Team Dynamics, so it was time to see if all the calculations were correct and see if they would fit, well mainly clear the lower suspension arm.

http://www.bebo.com/PhotoAlbumBig.js...oId=4621987944

As you can see for yourself the pictures in the link above that they do fit and they do clear, looks a little odd as the body isn't wide enough, but does look better with "bigger boots" the front also clear and we can turn lock to lock without hitting the anti rollbar or lower suspension arms as well, (unlike the other 2 racers)

The car is looking a bit untidy but thought i'd get some pictures before the rain started, will upload better pics once the front is finished off more and once the brakes are on the front as well.

Cheers Jon

craig · #2 20th July 2007, 19:25

John, that is starting to look very good! I love the wheels I think they are the ones I was going to get.

It does look so much better with wider rubber

Looking forward to seeing the new arches when they are done

Craig

Jon@JNRacing.co.uk · #3 20th July 2007, 21:08

Hi Craig

The Rims are worth every penny, but I do get them at a very cheap rate. Tyres weren't as cheap though but still. It looks better in the flesh at the mo, as its all being filled and smoothed over, but stil looks nice with big wheels, not sure what Mark or Terry will say when she opens the e-mail with the pictures attached. Could be interesting.

Body work i.e arche is being done around xmas so got a while to wait yet, but as soon as I get pics of anything that looks different, ill post them. Even if I do get told off for it.

Jon

grant620 · #4 21st July 2007, 17:01

Don't take this the wrong way...
But you do know that you won't have any more grip with wider rubber don't you?
9" is excessive.
You will not get heat into the tyres at the right rate and your actual contact patch will be no bigger than with a 7.5" rim.

Jon@JNRacing.co.uk · #5 21st July 2007, 18:38

Quote:

Originally Posted by grant620

Don't take this the wrong way...
But you do know that you won't have any more grip with wider rubber don't you?
9" is excessive.
You will not get heat into the tyres at the right rate and your actual contact patch will be no bigger than with a 7.5" rim.

As our car is having massive geometry changes, we were told that to run 230 slicks on the rear, we would need a 9" rim and after having meetings with specailists this is what we decided would be the best way to go. With regards to the grip, the grip factor on a 190-slicktofit a 15" rim which Mark races with, and the grip factor on 230- slick to fit a 17" rim, which we will be using, Is a rather large number.

grant620 · #6 21st July 2007, 18:59

You are saying that a 230 slick with the same force applied to it will have more grip than a 190 slick?
If so, go back and re-read your physics text books...
Force, area, pressure, etc
What I'm saying is that you don't need 230 slicks, nor do you need such wide rims.
I'm working on a 500+hp car at the moment that has 8" rims (against my better judgment) with 225 road tyres (a lot narrower than 230 slicks).
I would guarantee that this will have more grip than a 9" rim with 245 rubber.

Jon@JNRacing.co.uk · #7 22nd July 2007, 13:36

What your saying makes no sence. If what you are saying is try then why do all the high performance manufactures fit wider tyres? What we have done is done through the way our exi is being changed, evo'srace around in the saloon championship on 225 tyres ok they are 4wd and they are around 400-450bhp but because of the way the exi is designed with wieght balance etc its why we are doing it. Not jsut becasue it looks better or becasue we want to, its because the car isn't stable and needs it to stay on the track.

If you would like to talk to Avon Motorsport and tell them that there data sheets are wrong, and that a wider bigger tyre has no more grip (which is what you are saying) then please do.

This post was to show peope the finsihed rear developments that we have done at this stage, rather than to ask if it needs to be fitted or does an exi need more grip etc etc.

craig · #8 22nd July 2007, 14:54

Quote:

Originally Posted by grant620

Don't take this the wrong way...
But you do know that you won't have any more grip with wider rubber don't you?
9" is excessive.
You will not get heat into the tyres at the right rate and your actual contact patch will be no bigger than with a 7.5" rim.

Grant, this strikes me very much like my recent clutch issues!!

I am not up on physics and after my clutch dont care but I know of an elise that was running 215 rears and was untracktable up until 3rd gear with a recently fitted Jackson but he has since gone to 245 rear (not sure of the exact sizes but know he went up 3 sizes) and now the car grips like a bastard, even in 2nd it only scrabbles now......

There is also lateral grip to take into account 9" wide rubber will let go a lot later than 5.5" rubber around a track.

Like Jon said Zonda's etc are not fitted with 335's etc just for the looks

alackofspeed · #9 22nd July 2007, 21:16

The proof will be how it performs on track, and as the factory cars will soon be running low pressure turbos, there should be little power difference between Jon's and Mark's. They'll have to swap cars, and see how the lap times compare. Not totally scientific, but a reasonable way of demonstrating the performance differences.

craig · #10 22nd July 2007, 22:06

Quote:

Originally Posted by alackofspeed

The proof will be how it performs on track, and as the factory cars will soon be running low pressure turbos, there should be little power difference between Jon's and Mark's.

K series turbo's hmmm they will last 5 minutes then..........actually better make that 3

limpabit · #11 23rd July 2007, 06:08

I heard it was the 1.6 VTEC they turbo'ed.

On the Rover Forum, there's a Honda guy with one of these engines. Forged internals etc. 300 BHP with more to go out of one of these. Cost lots though at a guess.

Jon@JNRacing.co.uk · #12 23rd July 2007, 07:44

Dylon has the turbo on his at present and Mark should have his on for the race on 4th August. Both of there cars are ment to have 218BHP, we only have 197, so are on paper slower, but it will make some very interesting racing next year.

Ill be whilling to drive Marks and put a lap time down but not too keen on Mark driven ours with his current track record, haha.

Will be good to see both cars have a good run with the turbo's on a grippy track, as most the races so far have been crap weather.

They are using a standard Honda B16 Engine and have just bolted a turbo onto it, could do with some Vtec Killer cams though.

alackofspeed · #13 23rd July 2007, 15:21

I know a chap running a B-series honda engine, with over 500bhp! They are tough engines, and the heads flow remarkably well!

I wouldn't be surprised if an OEM spec K20A2 makes a better power curve, (not talking peaks) than a FI standard B16. Who mapped the B16 turbo?

alackofspeed · #14 23rd July 2007, 15:22

Quote:

Originally Posted by craig

K series turbo's hmmm they will last 5 minutes then..........actually better make that 3

The Rover 75 is (was?!) available with a 1.8 turbo k-series! Grenade?

Jon@JNRacing.co.uk · #15 24th July 2007, 13:04

Not sure on who mapped them, but I doubt they are set up correctly. When we tune ours it wilo go onto a dyno to be set up correctly and have the ecu mapped, as we will have Vtec Killer cams at that point along with a few other bits and pieces.

grant620 · #16 30th July 2007, 00:37

Quote:

Originally Posted by Jon@JNRacing.co.uk

What your saying makes no sence. If what you are saying is try then why do all the high performance manufactures fit wider tyres? What we have done is done through the way our exi is being changed, evo'srace around in the saloon championship on 225 tyres ok they are 4wd and they are around 400-450bhp but because of the way the exi is designed with wieght balance etc its why we are doing it. Not jsut becasue it looks better or becasue we want to, its because the car isn't stable and needs it to stay on the track.

If you would like to talk to Avon Motorsport and tell them that there data sheets are wrong, and that a wider bigger tyre has no more grip (which is what you are saying) then please do.

This post was to show peope the finsihed rear developments that we have done at this stage, rather than to ask if it needs to be fitted or does an exi need more grip etc etc.

OK, do the maths.
You will have no more force per sq cm by increasing the contact patch as the same mass will be pushing on the tyre, but spread over a larger surface area.
This means, no more grip.
Also, whether a larger tyre actually gives a larger contact patch is up for debate. It all depends on the structure of the tyre and pressures within.
You need the tyre to deflect a certain amount to get the contact patch to increase.
However, you will see more lateral grip (if that is a problem on the Marlin??) as the contact patch will be wider.
The tyre width you NEED is:
a) Wide enough to disperse the heat produced
b) Narrow enough to produce heat to get tyre up to temperature.

Go too wide and the tyre will not heat up, go too narrow and the tyre will not be able to get rid of the hear produced.

So that's a whole other argument as well!

In summary, there is theory and practice.
In theory - mathematically - a wider tyre produces no more forward force (ie grip when accelerating), but will increase lateral (cornering) grip. But a 20% increase in width will not increase lateral grip by 20%...
In practice - from experience - the tyre width needs to be chosen from trial and error.

For example:
Tomcat race cars (Rover 220 coupe Turbos) have 210/620 rubber on them. I've tried wider with much higher powered cars than the "series" cars, and not had the same grip afforded as the 210 rubber.
So, the guys at Roversport must have chosen 210 for a reason!!!

At the end of the day Jon, you do whatever you want - I'm sure you have already.
I'm only trying to provide some information/advice based on experience.