Need Tire Recomendations on 15x8 and 15x10

1stgear · 11-29-2016, 05:55 AM

I'm going to change out from my 17" rims and run some 15". My car is a 1985 M491 widebody with the rear spacers removed.

Here's what I'm running now:
FRONT: 17x9 255/40 R17
REAR: 17x11 315/35 R17

Here are the wheel specs on the new wheels:
FRONT: 15x8, 5x130, et10.6
REAR: 15x10, 5x130, et-5

Here are the tires I'm thinking about running. My question is will these be a good fit for the rims?
FRONT: 225/50 R15
REAR: 275/50 R15

Fly911 · Fly911's Garage

Street or track? For track use check out Hoosier, 225/50-15 and 275/35-15. For street use check out Michelin TB15, 18/60-15 (225/50-15) and 26/61-15 (285/40-15). All these 15 inch tires will have slightly smaller diameter than your 17 inch tires.

1100sport · 11-29-2016, 08:00 AM

On 10inch Wheel, the TB15 23/60-15 is a better fit IMO (270-40-15).

By any chance are you runing the campagnolo replica from Group4wheel?

1100sport · 08:06 AM

Another option is the Michelin MXW 255/45R15 93 W. It was designed for 10inch wide rim and was the tire of choice for the Alpine A310 V6, another rear mounted engine sportscar. The only issue is that there is no corresponding tire for the front - you will have to use another tire manufacturer if you go that path. But 225/50-15 are not difficult to come by.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by 1stgear

I'm going to change out from my 17" rims and run some 15". My car is a 1985 M491 widebody with the rear spacers removed.

Here's what I'm running now:
FRONT: 17x9 255/40 R17
REAR: 17x11 315/35 R17

Here are the wheel specs on the new wheels:
FRONT: 15x8, 5x130, et10.6
REAR: 15x10, 5x130, et-5

Here are the tires I'm thinking about running. My question is will these be a good fit for the rims?
FRONT: 225/50 R15
REAR: 275/50 R15

The differential between tire OD front to rear is on the high side ~23.9f & 25.5r

I'd want a little more front tire than a 225
Pirelli P7 Corsa Classic has

235/45 @~23.3x237 on an 8 & either 285/40 @~23.7x292 on a 10 or 305/35 @~23.3x305 on a 10

1stgear · 11-29-2016, 12:20 PM

Thanks everyone. So many options.

I guess I should have said that I want as much meat on the height as possible.

This will be for street use only. The rims are Fifteen52 Outlaws.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by 1stgear

Thanks everyone. So many options.

I guess I should have said that I want as much meat on the height as possible.

This will be for street use only. The rims are Fifteen52 Outlaws.

by meat I assume you mean section width and tread width

the wheel wheels were originally designed around 185/70x15 tires thatw ere ~25.3" tall and ~8" section width when mounted on a 6" wheel and have ~6.5" of tread

from the side this size fill the wheel well pleasingly

over the years the wheel wheels particularly in back became wider but they were still designed for a tire ~25" tall. Not only the visual but the practical is also designed around that tire height, trans gear ratios/cwp and torque curves all work harmoniously.. when any of them are changed the effect on that harmony is jeopardized

stuff a 3.6 in where a 2.4 once resided and the tires are undersized the trans is geared too short and harmony is destroyed,

any change will usually want at least one and often multiple other changes to restore harmony

'85 911 w/ 3.2 n/a engine and stock trans gearing was designed around 225/50 x16 tires, it was slightly under-geared because of fuel economy regs set by the US gov't, so It responds well to a slightly shorter 245/45 x16 tire. The difference in tire height is only ~.2" but is easily discernible by the driver.

If I were doing this I'd make every effort to use a tire that was no taller than a 225/50 @~24.9" and aim for shorter. Even if I had to give up some width. On the street the extra width isn't adding much anyway, only at 10/10ths on a track is it going to be worth more.

LUFTKUL · 11-29-2016, 01:52 PM

Email the guys at Group 4: info@group4wheels.com They have access to some wide 15" tyres in the UK they were willing to sell and ship reasonably.

gumba · 11-29-2016, 04:15 PM

The Michelin 270/40/15's are very tall tires compared to the 215's, 285's and 335's. All the TB's are around 24" tall, except the 270's which are 25.5"+ tall.
I'd run the 215's (actually more like a 225) on the front and the 285 rears.

Bleedsblue · 11-29-2016, 04:17 PM

Quote:

Originally Posted by 1stgear

So many options.

LOL, are you serious? There are zero options for a daily-able tire where it rains/gets cold.

Either way this sounds like an epic set-up; pictures will be required!

1stgear · 11-30-2016, 05:00 AM

Quote:

Originally Posted by Bleedsblue

LOL, are you serious? There are zero options for a daily-able tire where it rains/gets cold.

Either way this sounds like an epic set-up; pictures will be required!

I just had no idea there'd be so many options on widths and heights to choose from. LOL

I was originally going to run Nittos on the rear and Proxys on the front. Now I'm thinking hard on those Michelins.

I'll be sure to post up some pics when I have the new wheels on her. Here's how the car sits on the 17s:

1stgear · 11-30-2016, 05:03 AM

Quote:

Originally Posted by Bill Verburg

'85 911 w/ 3.2 n/a engine and stock trans gearing was designed around 225/50 x16 tires, it was slightly under-geared because of fuel economy regs set by the US gov't, so It responds well to a slightly shorter 245/45 x16 tire. The difference in tire height is only ~.2" but is easily discernible by the driver.

Hey, Bill.
Excellent info! My car is a ROW, not US. Does that make any difference on gearing or were all cars the same?

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by 1stgear

Hey, Bill.
Excellent info! My car is a ROW, not US. Does that make any difference on gearing or were all cars the same?

US cars of that era have shorter gearing than the RoW cars in 4 & 5, same in 1 & 3 taller in 2
here's a comparison of speed in gears, same tires, same revs
US '84-86
39 70 99 125 159
RoW '84-86
39 68 99 130 164

1100sport · 11-30-2016, 07:36 AM

I dont think your statement is correct. See the michelin site:
TB15 | Michelin Classic
or
Michelin TB15 | Longstone Tyres

the difference in overall diameter between the 23/62-15 and the larger sizes is very limited: 625mm versus 615mm. I dont think you can visually see the difference unless you put one tire on the other, and even then... :-)

Here is a picture of my car fitted with the 270/45-15, they dont look "out of synch" with the front tires IMO

Quote:

Originally Posted by gumba

The Michelin 270/40/15's are very tall tires compared to the 215's, 285's and 335's. All the TB's are around 24" tall, except the 270's which are 25.5"+ tall.
I'd run the 215's (actually more like a 225) on the front and the 285 rears.

1100sport · 11-30-2016, 07:38 AM

see the stance of the car with 215/55-15 and 270/45-15 TB15

1100sport · 11-30-2016, 07:50 AM

BTW I am also using the larger 26/61-15 TB5 tires on 11x15 Gotti during track days.

gumba · 11-30-2016, 07:53 AM

The 270 sizing may have changed since I had mine in 2014. I've used the TB's in various sizes on a couple of different cars. The 215's on the front, and the 270's, 285's and currently 335's on 13 x 15 Fuchs on the rears.
To me, the 270's were noticably taller. I tried them on the front, no go too high. Then I tried them on the back mounted on 11x15 Fuchs, Still didn't look right.

Bleedsblue · 11-30-2016, 10:00 AM

Quote:

Originally Posted by 1stgear

I just had no idea there'd be so many options on widths and heights to choose from. LOL

I was originally going to run Nittos on the rear and Proxys on the front. Now I'm thinking hard on those Michelins.

I'll be sure to post up some pics when I have the new wheels on her. Here's how the car sits on the 17s:

No question to me, the fatty 15" will always look more proper than wide, thin 17s.

You must have had good experiences with the Fifteen52s to order another set, huh? I have a set of their cast wheels on my BMW and love 'em, and have it on my bucket list to pick up a forged set of their stuff in some style eventually. But $$$.

1stgear · 11:19 AM

1100SPORT - your car is bada$$.

I was looking at Nittos in the 275/50 and Proxys for the 225/50. I really like the TB15s - but dang are they pricey. Are they worth the extra cost?

Brent - yes, I really like Fifteen52. Excellent customer service and I'm very pleased with their products. Haven't decided if I'll sell the 17s or just hold on to them. I also have a set of 17" Zuffenhaus Fikse fuchs. I wasn't impressed with Fikse's customer service at all. Zuffenaus had good CS, but they don't control manufacturing of the wheels. Plus, I had to pay up front. Fifteen52 and Forgeline only require half down and the remaining balance upon completion. I like that because it leaves some skin in the game for them to finish the job.

1100sport · 11-30-2016, 01:37 PM

The TB15 is a great tire. The level of grip is mind blowing - very close to that of a proper race tire. On the street, you would be crazy to reach the limit of such tires, which also means that they give a lot of confidence. You can feel you can rely on them, and they will also be very forgiving if you enter too fast in a corner...
The only thing which requires some getting used to is the tire wall, not as rigid as some other track day tires would give you. My understanding is that the Michelin engineers have désigned this relatively soft wall on purpose so as to not put excessive stress on the chassis. Remember that these tires are to be fitted on 30+ years old cars and that with the amount of grip they offer, they could simply destroy the chassis... in short you will not be desappointed but they are pricey.