ISF on 18inch Track Wheels

Jon Dee · August 24, 2023

Thanks for the pics... your car looks good on 18's. If you don't mind me asking, what size tires are you running, and what is your suspension setup ?

Also, I haven't been able to find any fender arch to ground measurements for an ISF on OEM suspension. I'd like to be able to compare the height of my car with the factory stock height so that I can see where I might end up with Swift springs and 18" wheels. If you have any measurements that would be most helpful :smile:

On 18's I would likely be running 225/40 on 8" rims in front and 255/35 on 9" rims in back. I suspect that the factory engineers knew what they were doing when they decided what wheels and tires they wanted on the car, so apart from a 1" downsize in diameter I would stay with the factory widths and aspect ratios.

Cheers...

RichGS11 · August 24, 2023

Hey dude.

I'm on 275 35 18's. Square set up all round as the guys I know that do autocross in the States all rate the square set up which eliminates understeer. In fact, from vendors to those doing track days and autocross, I don't know of any on staggered set ups. I'm 9.5 wide all round and I'd say the 275's are a nice all-rounder. There might be better evidence out there that the stock sizes are better, but I'm yet to see it. I know I put the power down better with wider rears and the handling for our twistie B roads here in the UK is spot on, so I can only talk from what I have.

I'm currently on BC coilovers which have been corner weighted and balanced. They're not my preferred option but due to availability and previous experience, plus my OEM shocks were on their way out, I needed a quick fix. I have to say they're performing well at the moment.

Jon Dee · August 24, 2023

I sold my E92 335i before picking up the ISF. The cars are quite similar in size and weight, except the ISF has more weight up front. The E92 ran 225/40-18 and 255/35-18 and that worked quite well for "spirited" driving. I used that car for a few car club events, sealed hillclimbs and street sprints. But I don't plan using the ISF for any events, so maximum grip and handling is not a priority. My favoured tire is the Bridgestone RE003 and unfortunately they do not offer it any wider than 255 in 18" size. If they did I would go with 235 in front and 265 in back.

When I get to the point of buying wheels and tires I will have a look at available offsets, rim widths and tire brands and choose whatever combination I hope will give acceptable handling and a quiet ride. I don't mind the stiffer suspension... that is something that goes with sportscar type handling. I just want to get rid of the clunks, bangs and rattles !!!!! Next move is to get the car up on ramps so that I can see if there is anything worn/loose/broken underneath that could be generating noise.

Cheers...

ubersonic · August 24, 2023

The biggest problem with dropping to 18" (aside from most wheels that look good on an ISF looking better in 19") is that unless you're okay with your tyre diameter/circumference (and thus your speedo/VDIM) being a bit out of whack then you have to fit 255/40/18 and 225/45/18 which means tyre choice is simply inferior to what you can get in 19".

RichGS11 · August 24, 2023

14 minutes ago, ubersonic said:

The biggest problem with dropping to 18" (aside from most wheels that look good on an ISF looking better in 19") is that unless you're okay with your tyre diameter/circumference (and thus your speedo/VDIM) being a bit out of whack then you have to fit 255/40/18 and 225/45/18 which means tyre choice is simply inferior to what you can get in 19".

I was concerned about that and well worth taking note, but Asymmetric 5's wiped that fear out of the park very quickly. I couldn't get PS4S's in 18", but I'm not bothered now. It's just a case of shopping around and seeing what's on the market. There's always a suitable replacement.

RichGS11 · August 24, 2023

8 hours ago, Jon Dee said:

I sold my E92 335i before picking up the ISF. The cars are quite similar in size and weight, except the ISF has more weight up front. The E92 ran 225/40-18 and 255/35-18 and that worked quite well for "spirited" driving. I used that car for a few car club events, sealed hillclimbs and street sprints. But I don't plan using the ISF for any events, so maximum grip and handling is not a priority. My favoured tire is the Bridgestone RE003 and unfortunately they do not offer it any wider than 255 in 18" size. If they did I would go with 235 in front and 265 in back.

When I get to the point of buying wheels and tires I will have a look at available offsets, rim widths and tire brands and choose whatever combination I hope will give acceptable handling and a quiet ride. I don't mind the stiffer suspension... that is something that goes with sportscar type handling. I just want to get rid of the clunks, bangs and rattles !!!!! Next move is to get the car up on ramps so that I can see if there is anything worn/loose/broken underneath that could be generating noise.

Cheers...

In reference to clunks and bangs, I had an odd and intermittent knocking from the front left of my car which ended up being the strut (hence the coilover upgrade). They are noisey when they go and worth a look. Plus as with all things old, the vulnerable bits start to perish, so rubbers and ball joints are a good go to, notably the front lower ball joints. Cheap and easy to replace too.

Jon Dee · August 24, 2023

Yes... my car has close to 200,00km and 15 years on rubber bushings and all moving parts, so I will be looking to see what needs refreshing in the suspension linkages. I'll also be looking at the HKS coilovers to see if they have a problem. The PO mistakenly ran them set at full hard from the time of installation, and that may have caused some damage. I have the OEM shocks assemblies, but given the criticism levelled at them back in 2008, I intend to install Bilsteins instead of reusing the OEM units.

ubersonic I had to look up VDIM to see what that was :smile: Seems that keeping wheel speeds front and rear close to the same is likely the most important input. That is something I will keep in mind when I make a decision on tires. The combination that you suggested above would be OK by me... a bit more sidewall is good for comfort

Cheers...

Jon Dee · August 25, 2023

Couldn't see any way to edit my last post, so this is just an after thought... looking back through the PO's notes I see this listed among the maintenance work that had been carried out "GSF/RCF Front LCA Bushings". Is it safe to assume that this will be adequate for normal road use ?

Cheers...

RichGS11 · August 25, 2023

5 hours ago, Jon Dee said:

Couldn't see any way to edit my last post, so this is just an after thought... looking back through the PO's notes I see this listed among the maintenance work that had been carried out "GSF/RCF Front LCA Bushings". Is it safe to assume that this will be adequate for normal road use ?

Cheers...

Yes definitely. They were made a little stronger than the ISF's partly down to the weight of the newer models. They'll be great for the road and they've also been replaced which is great.

Jon Dee · August 28, 2023

Been looking at wheels and doing a bit more research. Read that the ISF is prone to wearing the inside edge of tires when slammed. Mine is lowered (not exactly sure how much) and runs a little over 2deg of negative camber on the front, whereas I would normally be happy at about 1.5deg. The existing 19" wheels are sitting quite nice, so I'm thinking if I decide to go with 18's I would stick with the same widths and offsets, raise the car a little and step up to my currently preferred setup of 235 or 245/40 in front and 265 or 275/35 in back.

One set of WORK replicas I quite like are shown in the pics attached. I believe they have exactly the same widths and offsets as the exiting 19's. With this setup the wheels would be a bit further away (down) from the guards, stand up a little straighter, and the sidewalls would be a fraction taller. Does this sound like a plan, or am I missing something ??

Cheers...

Jon Dee · September 2, 2023

On 8/28/2023 at 7:04 PM, Jon Dee said:

One set of WORK replicas I quite like are shown in the pics attached. I believe they have exactly the same widths and offsets as the exiting 19's. With this setup the wheels would be a bit further away (down) from the guards, stand up a little straighter, and the sidewalls would be a fraction taller. Does this sound like a plan, or am I missing something ??

Not a plan. Doing a bit more checking and measuring, I can see that the combination of 9.5 rear wheel width, 38 offset and ride height meant that the PO could not fit anything wider than 265/30-19 tyres without rubbing. Coilovers are already set to maximum height and I'm not going to roll the guards. So I'll be looking for a new set of wheels with higher offset to move the wheels inwards a little.

Cheers...

Jon Dee · September 25, 2023

It's always good to have a plan B :smile: As it happens I found someone selling a really clean set of OEM 19" ISF wheels with good factory size rubber, so I bought them. Now the idea is to get them and the Bilsteins installed on the car so I can see just how bad or good the ride is with 19" wheels. Changing to 18" wheels will have to wait until the jury returns its verdict !!

Cheers...

Jon Dee · November 13, 2023

On 8/24/2023 at 6:02 PM, RichGS11 said:

Whilst I have heard some wheels have clearance issues, I can tell you that's limited to a few designs. Here's my car on Wedsports SA25R'S and Enkei GTC01RR's (the side shot being the current set up and the Enkeis).

There are a set of these RS05RR wheels for sale locally... 18 x 9 ET35. Got me thinking about square setups again, and was wondering if they would work on my car ? With 18 x 9.5 on your car, what ET do your wheels have, and are they the same ET front and rear ?

Do your front wheels/tyres poke out past the guards when viewed from above ?

Cheers...

Jon Dee · November 16, 2023

On 11/13/2023 at 7:16 PM, Jon Dee said:

There are a set of these RS05RR wheels for sale locally... 18 x 9 ET35.

Link died on me !!!

RichGS11 · November 16, 2023

My set up are 18x9.5 et35 (square set up) I had to shave down the rears but I wanted the fitment an exact way.

There are probably better set ups if you wish to not touch bodywork (preferred).

Jon Dee · November 16, 2023

10 hours ago, RichGS11 said:

There are probably better set ups if you wish to not touch bodywork (preferred).

Yeah... been a bit torn between the mega flush look and the real reason that I'm even considering going to 18's :no2: So I am moving away from low ET combinations and back to conservative sizing that will allow me to get a bit more sidewall and a little more width without any clearance issues. I'd like to end up with something like 18 x 8.5 ET45 in front with 235/45 and 18 x 9.5 ET55 with 265/40 in back... or close to that depending on wheel availability.

Hopefully that will soften the ride and reduce tyre thump a tad more. Thanks for your input :smile:

Cheers...

Evogixer · November 29, 2023

I've been running 18 x 9.5 et45 all round for 3yrs now. RAYS listed this ISF fitment in their info. Perfect fit with 275/35's, no mods |& no understeer with a better ride & a lot more grip. Stock height. They look awesome & proper flush too. Couldnt be happier. I used this for calculations: https://www.willtheyfit.com/

Jon Dee · November 29, 2023

Thanks Andy... that's the kind of information I have been looking for About 12 hours ago I bought a cheap set of wheels 18 x 8.5 ET38 to experiment with. Probably will try 235/45 in front and 255/40 in back. That will give me enough information to decide if I want to invest in custom wheels and more rubber on the road.

Did you have to nip and tuck anything to allow the 275's to fit without rubbing ?

Cheers...

Jon Dee · December 13, 2023

I've got the wheels now and have checked them out... look to be OK. As this is really just an experiment, I've decided to get a set of cheap 255/40-18's mounted to satisfy my curiosity regarding looks, fit, ride and square vs staggered. After I have driven this for a while I will decide on the next step

Cheers...

Jon Dee · February 6

Got 255/40-18's mounted all round and wheels installed on the car today. Initial short drive didn't show any dramatic difference to the 19" factory wheels, but as expected the new rubber is quieter than the old Potenzas. Happy with the fit and look, so now just need to get an alignment and then on with the onerous task of putting some miles on the new setup :wink3: