15" for a 3rd gen?
10-09-07, 09:46 AM
#1
15" for a 3rd gen?
Any chance I could get a steel custom made 15 rim to fit my 3rd gen stock hubs/caliper? Has anyone tried this?
Why asking? Hoosiers makes a 275/35/15. Outside diameter is 23. Outside diameter of a 245/45/16 is 24.4 The shorter 275/25/15 equates to a 6% gear reduction. I run the car in SCCA Solo Street Prepared. Mechanical gear changes are verboten in the class while wheel size is unrestricted. Using the 275/35/15 would be equivalent to substituting the stock 4.10 final drive with a 4.35. 4.35 is not the highly desirable 4.77 but it would still help I think. Besides, the wider footprint would also be nice to have together with the lower CG and polar moment of inertia
Thanks
- Sandro
Why asking? Hoosiers makes a 275/35/15. Outside diameter is 23. Outside diameter of a 245/45/16 is 24.4 The shorter 275/25/15 equates to a 6% gear reduction. I run the car in SCCA Solo Street Prepared. Mechanical gear changes are verboten in the class while wheel size is unrestricted. Using the 275/35/15 would be equivalent to substituting the stock 4.10 final drive with a 4.35. 4.35 is not the highly desirable 4.77 but it would still help I think. Besides, the wider footprint would also be nice to have together with the lower CG and polar moment of inertia
Thanks
- Sandro
10-09-07, 10:29 AM
#2
Lives on the Forum
I'd look in the drag race sub-forum, there's bound to be guys there wanting to run 15" drag slicks thinking up ways to do this. You could also measure up the brakes and send the measurements and the requested wheel sizes to custom wheel makers like Kodiak and see what they say.
10-12-07, 07:04 AM
#4
I'd look in the drag race sub-forum, there's bound to be guys there wanting to run 15" drag slicks thinking up ways to do this. You could also measure up the brakes and send the measurements and the requested wheel sizes to custom wheel makers like Kodiak and see what they say.
Thank you for the lead. -Sandro
I had asked John already but he indicated they cannot make anything smaller than 16". Thank you for your suggestion anyhow. - Sandro
05-12-08, 09:06 PM
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Offsets?
I was thinking of picking up a new set of wheels and tires for some asp action this year... wondering about what the offsets would be, I think the folks over at http://www.diamondracingwheels.com/ could hook me up with something inexpensive to meet my needs...
Anyone have the proper offset numbers to run the hoosier on a 15"
Dan
Anyone have the proper offset numbers to run the hoosier on a 15"
Dan
05-13-08, 07:42 AM
#7
Dan,
Bill at Diamond has been very helpful in trying to fit one of their 15x10 wheels.
He sent me one their "Pro" wheels with a 5" backspace to "try on". These are the issues.
Their wheels have a narrower section where the wheel dish is welded on - dropwell or drop center - which has a 13.30" ID. That is not enough to clear the brakes. Based on my measurements, you need close to 14" clearance to fit them inside (I measured 6.9" from the hub center to the outer part of the brake caliper. Up to the dropwell (from the inside of the wheel - called "bell") there is no problem as the "bell starts at almost 15" at the inside lip then slopes down to 14"+ when the transition to the dropwell starts. What I found out is that with a 5" bs the caliper touch the start of the dropwell. I then added spacers until I cleared the brake calipers and found out I needed 0.5" more - or a 4.5" backspace. Since the OE wheel has 6.5" bs, with 4.5" you would have the wheel sticking out 4". In order to "simulate" it and check any interference with the fenders, I mounted 4 x 1" spacers, then a OE wheel with a V710 215/40/16 tire on (22.6" OD vs. 23.0" of the Hoosier 275/35/15 we are aiming at). I also removed all the plastic liners inside the fender. Because of the 4" spacers, when turning the steering wheel, the tire edge now moves along a wider arc when you turn the steering wheel. Unfortunately. this creates two severe interferences. When the wheel is turned to the right, the tire interferes with the lower part of the fender (a plastic material), the plastic ducts to the brakes and, even worst, it is dangerously close to the edge of structural metal sheet. Turning the wheel to the left, the tire cannot ive enter the well, because the rear outside edge of tire interferes with the lower part of the fender - all metal.
After talking with Bill yesterday, he suggested to try another wheel - the "SS" which has a longer bell, with a minimum 14" ID. On that one, he could make a backspace of 6". That would make the wheel stick out "only" 2.5" more than OE. With that, there may be little (requiring minor modifications to solve it) or no interference with the fenders at all. It also remains to be seen if the brake caliper will clear or still would hit the transition to the dropwell. Stay tuned and I will keep you posted.
- Sandro
Bill at Diamond has been very helpful in trying to fit one of their 15x10 wheels.
He sent me one their "Pro" wheels with a 5" backspace to "try on". These are the issues.
Their wheels have a narrower section where the wheel dish is welded on - dropwell or drop center - which has a 13.30" ID. That is not enough to clear the brakes. Based on my measurements, you need close to 14" clearance to fit them inside (I measured 6.9" from the hub center to the outer part of the brake caliper. Up to the dropwell (from the inside of the wheel - called "bell") there is no problem as the "bell starts at almost 15" at the inside lip then slopes down to 14"+ when the transition to the dropwell starts. What I found out is that with a 5" bs the caliper touch the start of the dropwell. I then added spacers until I cleared the brake calipers and found out I needed 0.5" more - or a 4.5" backspace. Since the OE wheel has 6.5" bs, with 4.5" you would have the wheel sticking out 4". In order to "simulate" it and check any interference with the fenders, I mounted 4 x 1" spacers, then a OE wheel with a V710 215/40/16 tire on (22.6" OD vs. 23.0" of the Hoosier 275/35/15 we are aiming at). I also removed all the plastic liners inside the fender. Because of the 4" spacers, when turning the steering wheel, the tire edge now moves along a wider arc when you turn the steering wheel. Unfortunately. this creates two severe interferences. When the wheel is turned to the right, the tire interferes with the lower part of the fender (a plastic material), the plastic ducts to the brakes and, even worst, it is dangerously close to the edge of structural metal sheet. Turning the wheel to the left, the tire cannot ive enter the well, because the rear outside edge of tire interferes with the lower part of the fender - all metal.
After talking with Bill yesterday, he suggested to try another wheel - the "SS" which has a longer bell, with a minimum 14" ID. On that one, he could make a backspace of 6". That would make the wheel stick out "only" 2.5" more than OE. With that, there may be little (requiring minor modifications to solve it) or no interference with the fenders at all. It also remains to be seen if the brake caliper will clear or still would hit the transition to the dropwell. Stay tuned and I will keep you posted.
- Sandro
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05-16-08, 03:01 PM
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Thanks Sandro for all that legwork, I hope it works out.... I had been running my 7 in ASP for a few years, but left it to go karting; the car really needed some better tires though to run in that class, I hope we can get a fit...
I was thinking I might even go so far as to look for some replacement front fenders if I just needed a little more clearence... My 7 is in too good of condition to consider modifying the stock ones, but...
What do you think about the ride height with the wheel sticking out... I have coil overs on a set of GAB-R's they really dont have any sort of bump stop, I guess I would need to add something to ensure the tire never touched the fender
These are about 1cm wider than stock, thats probably not going to be enough.. http://www.seiboncarbon.com/pdut_det...asp?ItemID=657 but would be very nice none the less.
I live near Milwaukee, if Bill needs a car for fitment issues, let me know, I can probably arrange a trip into town.
Dan
I was thinking I might even go so far as to look for some replacement front fenders if I just needed a little more clearence... My 7 is in too good of condition to consider modifying the stock ones, but...
What do you think about the ride height with the wheel sticking out... I have coil overs on a set of GAB-R's they really dont have any sort of bump stop, I guess I would need to add something to ensure the tire never touched the fender
These are about 1cm wider than stock, thats probably not going to be enough.. http://www.seiboncarbon.com/pdut_det...asp?ItemID=657 but would be very nice none the less.
I live near Milwaukee, if Bill needs a car for fitment issues, let me know, I can probably arrange a trip into town.
Dan
05-16-08, 04:02 PM
#9
Hi Dan.
Replacing the entire fender is not allowed in ASP, that would bump you up to SM2. In ASP you can only modify fender and bumper with the only purpose of fitting your wheel of choice. Now, since the the Hoosier OD is only 23", and you have coilover, with decently stiff springs you may still be OK - obviously adding bumpstop would be good insurance. In the worst case, some lip rolling or moderate flares should be sufficient.
I should be receiving the SS wheel from Bill within days. He is tack welding the dish at 7" - after discussing this further with him I thought it would be worth trying and see if we can still clear the brake calipers. Note, with 7.5" backspace the rim would have the same offset than stock, meaning the wheel could probably be contained entirely within the fenders (for sure in the rear). With 7", the outside of the rim would be 1.5" out - as compared with the OE rim. Rear may still be OK but the front will likely stick but maybe just 0.5" You could use the fitting spreadsheet to calculate it more precisely.
As for you driving there and try fitting wheels, that may be a good idea. Although, I got the impression that their inventory of wheels "ready to try" is very limited and each one is basically custom made.
- Sandro
Replacing the entire fender is not allowed in ASP, that would bump you up to SM2. In ASP you can only modify fender and bumper with the only purpose of fitting your wheel of choice. Now, since the the Hoosier OD is only 23", and you have coilover, with decently stiff springs you may still be OK - obviously adding bumpstop would be good insurance. In the worst case, some lip rolling or moderate flares should be sufficient.
I should be receiving the SS wheel from Bill within days. He is tack welding the dish at 7" - after discussing this further with him I thought it would be worth trying and see if we can still clear the brake calipers. Note, with 7.5" backspace the rim would have the same offset than stock, meaning the wheel could probably be contained entirely within the fenders (for sure in the rear). With 7", the outside of the rim would be 1.5" out - as compared with the OE rim. Rear may still be OK but the front will likely stick but maybe just 0.5" You could use the fitting spreadsheet to calculate it more precisely.
As for you driving there and try fitting wheels, that may be a good idea. Although, I got the impression that their inventory of wheels "ready to try" is very limited and each one is basically custom made.
- Sandro
05-17-08, 10:38 AM
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Ah right then on the fender replacement.... Althought I would still need to pick up a replacement fedner to modify if required, but hopefully it wont come to that.
I would think the rear might run into control arm issues, I have custom ones but I dont think they give that much more clearence... Also I would assume you want to have the same track width in the front and rear, althought flaring the rear fenders is out of the quesiton for me.
Also I was wondering if you would need to go to a full 10" rim to run a 10" tire... might be able to run a slightly smaller wheel to get more clearance in close...
Dan
I would think the rear might run into control arm issues, I have custom ones but I dont think they give that much more clearence... Also I would assume you want to have the same track width in the front and rear, althought flaring the rear fenders is out of the quesiton for me.
Also I was wondering if you would need to go to a full 10" rim to run a 10" tire... might be able to run a slightly smaller wheel to get more clearance in close...
Dan
05-21-08, 01:29 PM
#11
I got the new wheel to try. 7" backspace unfortunately won't work. I say unfortunately because the tire would otherwise completely be tucked inside the fenderwells. I found two interferences: one is the usual brake caliper that hits the dropwell; second - and good thing that I am checking this thoroughly before placing an order this time - when the wheel is completely turned in, the inside of the rim touches the steering arm. I had to use two wheel spacers I have - 1/4" each I thought - to clear both issues. Then, I measured the spacers - which I thought were 1/4" each and they are actually 8.1 mm (or about 5/16") which is an odd number. So, I am getting a 1/2" spacer now to make sure that 6.5" work. If not, Bill will have to make me wheels with 6.36" backspace - custom wheels indeed. I know it sounds a little ridiculous but I am trying to work around three conflicting issues. clearing the steering rods, clearing the brake caliper and if possible avoid removing the splash liners inside the fenderwell. Obviously, it would be easier with a 9" wheel.
In the rear, there is only one issue that requires massaging. The head of the bolt that attaches the toe control arm to the upright needs to be ground out. With my 0.64" spacers, I found no other issues, everything is really tight but clear, including the top part of the upright and where the rear brake attaches to. It remains to be seen if all will still work with an even 6.5" backspace. And I hope that there will be no other suspension movements I may have forgotten to check.
Please let me know if other sources of possible interference come to your minds. Thanks
Slowly getting there...
- Sandro
In the rear, there is only one issue that requires massaging. The head of the bolt that attaches the toe control arm to the upright needs to be ground out. With my 0.64" spacers, I found no other issues, everything is really tight but clear, including the top part of the upright and where the rear brake attaches to. It remains to be seen if all will still work with an even 6.5" backspace. And I hope that there will be no other suspension movements I may have forgotten to check.
Please let me know if other sources of possible interference come to your minds. Thanks
Slowly getting there...
- Sandro
05-21-08, 09:42 PM
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Thats some great news...
The drop bolt on my racing beat adjustable rear sway bar can get close to the inside of the rim as I recall, if you use the stiff position its at an odd angle I think... your movements idea is a great one, I would think of spinning down the spring and using a jack to try to simulate the range of motion... The biggest issue however, will surely be up front can you get the entire 10" tire under the front fender or are you just looking at the wheel clearance now.
If this works, I am definitely up for a set, those diamond racing wheels are a real bargain anyways.
Dan
The drop bolt on my racing beat adjustable rear sway bar can get close to the inside of the rim as I recall, if you use the stiff position its at an odd angle I think... your movements idea is a great one, I would think of spinning down the spring and using a jack to try to simulate the range of motion... The biggest issue however, will surely be up front can you get the entire 10" tire under the front fender or are you just looking at the wheel clearance now.
If this works, I am definitely up for a set, those diamond racing wheels are a real bargain anyways.
Dan
06-15-08, 06:15 AM
#15
Done!
Diamond wheels Super Spun (SS) http://www.diamondracingwheels.com/superspun.html
15x10 with 6.5" backspace
Hoosier 275/35/15
Rim weight 21 lb
I had the stud holes cut at 60 deg (vs. their standard 45 deg cut) to use regular nuts.
Wheels stick out a bit but not much as you can see from pics.
Wheels fit right and clear brake calipers and all other hardware but the head of the nut holding the toe link in the rear. Fixed it with some grinding (about 2/3 out).
Autoxed yesterday. Didn't touch fender lip (I use 14Kg/mm springs all around), didn't rub fender liners.
Only problem - while testing before autox - with the wheels fully locked on left turn, could hear minor scratching. I suspect the steering tie rod touching the inside rim but could just be rubbing against the fender liner; not a concern for me, I don't lock wheels while autoxing.
- Sandro
Diamond wheels Super Spun (SS) http://www.diamondracingwheels.com/superspun.html
15x10 with 6.5" backspace
Hoosier 275/35/15
Rim weight 21 lb
I had the stud holes cut at 60 deg (vs. their standard 45 deg cut) to use regular nuts.
Wheels stick out a bit but not much as you can see from pics.
Wheels fit right and clear brake calipers and all other hardware but the head of the nut holding the toe link in the rear. Fixed it with some grinding (about 2/3 out).
Autoxed yesterday. Didn't touch fender lip (I use 14Kg/mm springs all around), didn't rub fender liners.
Only problem - while testing before autox - with the wheels fully locked on left turn, could hear minor scratching. I suspect the steering tie rod touching the inside rim but could just be rubbing against the fender liner; not a concern for me, I don't lock wheels while autoxing.
- Sandro
06-15-08, 04:24 PM
#16
Done!
Diamond wheels Super Spun (SS) http://www.diamondracingwheels.com/superspun.html
15x10 with 6.5" backspace
Hoosier 275/35/15
Rim weight 21 lb
I had the stud holes cut at 60 deg (vs. their standard 45 deg cut) to use regular nuts.
Wheels stick out a bit but not much as you can see from pics.
Wheels fit right and clear brake calipers and all other hardware but the head of the nut holding the toe link in the rear. Fixed it with some grinding (about 2/3 out).
Autoxed yesterday. Didn't touch fender lip (I use 14Kg/mm springs all around), didn't rub fender liners.
Only problem - while testing before autox - with the wheels fully locked on left turn, could hear minor scratching. I suspect the steering tie rod touching the inside rim but could just be rubbing against the fender liner; not a concern for me, I don't lock wheels while autoxing.
- Sandro
Diamond wheels Super Spun (SS) http://www.diamondracingwheels.com/superspun.html
15x10 with 6.5" backspace
Hoosier 275/35/15
Rim weight 21 lb
I had the stud holes cut at 60 deg (vs. their standard 45 deg cut) to use regular nuts.
Wheels stick out a bit but not much as you can see from pics.
Wheels fit right and clear brake calipers and all other hardware but the head of the nut holding the toe link in the rear. Fixed it with some grinding (about 2/3 out).
Autoxed yesterday. Didn't touch fender lip (I use 14Kg/mm springs all around), didn't rub fender liners.
Only problem - while testing before autox - with the wheels fully locked on left turn, could hear minor scratching. I suspect the steering tie rod touching the inside rim but could just be rubbing against the fender liner; not a concern for me, I don't lock wheels while autoxing.
- Sandro
