For those of you running 17's with big, meaty tires

[330icrazy]

I am using z4 hub with e30 bearing a caliper and rotor from a e46 325i. A bracket for the e46 caliper from srs. I am working on the fender clearance now but this is with a 255/40 r17.

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[LowR3V'in]

picture of front?

[330icrazy]

I will when I do it. Haven't got that far yet just started the right rear today

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[cwlo]

So I am running the 5 lug sleeve setup, and no flares, and have fitted 245/40/17's in the rear with a fender roll. Had to grind out the sealant in the fender lip before rolling, but the rears fit nicely with a 10mm spacer and z4 rear hub.


Fronts look like they will need more work. The 10mm spacer up front is not enough to give me enough clearance for the coilover adjuster, and also the frame rail at full lock. . I'm going to shim it with a few washers and see how it looks. So I'm figuring 12-15mm spacer, a good fender rolling, and then on to the valance and rear fenderwell. Even with flares, those areas will still be problematic.

[alistairolsen]

Why would you want 245 fronts?

[amcp]

Why wouldnt you?

[alistairolsen]

Because E30s have lovely steering, arent generally prone to understeer when set up correctly and too big a tyre doesnt help anything really. Find me an example of a high performance RWD car which wears the same tyre size front and rear, especially one which wears 245s on the front of an 1100kg car.

[iansane]

Because E30s have lovely steering, arent generally prone to understeer when set up correctly and too big a tyre doesnt help anything really. Find me an example of a high performance RWD car which wears the same tyre size front and rear, especially one which wears 245s on the front of an 1100kg car.

There aren't a bountiful amount of rwd 1100kg cars out there that are performance oriented, let alone ones that manufacturers haven't made concessions on things like tire sizes. Or were you talking non stock cars?


I can't get passed that statement, "too big of a tire doesn't help anything really" I don't even know what to say to that. Those words short circuited my brain. I mean, I know you can't have a blanket statement but how in the world could 245s, or even larger, not benefit? (obviously we're talking when the rest of the car is properly setup to match having larger rubber and not just bolted on to a stock car.)

Having said that, I run 255s on 17s with mild flares. So obviously I'm biased.

[330icrazy]

I want as big of a tire that I can fit. Going wider is proven to be faster in autox I am going to run a 235 because I don't want flares.

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[Victell]

Its pretty simple, steering feel vs maximum traction.

While both are valid pursuits it is ultimately the driver's preference.

[LowR3V'in]

i wish i had 245 fronts today when i locked them up

[bradmer]

There aren't a bountiful amount of rwd 1100kg cars out there that are performance oriented, let alone ones that manufacturers haven't made concessions on things like tire sizes. Or were you talking non stock cars?


I can't get passed that statement, "too big of a tire doesn't help anything really" I don't even know what to say to that. Those words short circuited my brain. I mean, I know you can't have a blanket statement but how in the world could 245s, or even larger, not benefit? (obviously we're talking when the rest of the car is properly setup to match having larger rubber and not just bolted on to a stock car.)

Having said that, I run 255s on 17s with mild flares. So obviously I'm biased.

May I ask that you post your wheel fitment details? I get 235/40/17 et25 under there with a fender roll and no spacers, but it's really close to rubbing on the struts up front and inside on the rears. Car is lowered.

[alistairolsen]

There aren't a bountiful amount of rwd 1100kg cars out there that are performance oriented, let alone ones that manufacturers haven't made concessions on things like tire sizes. Or were you talking non stock cars?


I can't get passed that statement, "too big of a tire doesn't help anything really" I don't even know what to say to that. Those words short circuited my brain. I mean, I know you can't have a blanket statement but how in the world could 245s, or even larger, not benefit? (obviously we're talking when the rest of the car is properly setup to match having larger rubber and not just bolted on to a stock car.)

Having said that, I run 255s on 17s with mild flares. So obviously I'm biased.

General trend of all RWD performance cars in recent history, from every BMW M car, Lotus, small volume track cars, every example of a RWD performance car uses wider rears than fronts. I'm not suggesting not maximising rears (I've got 245s to on on mine) but I simply cant see the need for wedging that same tyre size under the front.


Lotus Elise cup 260 862kg 250bhp 205/46 16 front 235/40 17 rear

Lotus Europa S 995kg 225bhp 195/47 17 front 235/40 18 rear
Lotus Evora 1248kg 280bhp 225/40 18 front 255/35 19 rear


BMW 1M 1495kg 340bhp 245/35 19 front 265/35 19 rear


KTM Xbow 790 kg 300bhp 205/40 17 front 235/40 18 rear


Ariel Atom 621kg ~300bhp 195/50 15 front and 225/45 16 rear


986 Cayman 1295kg 300bhp 225/40 18 front and 265/35 18


I could carry on, but the generall trend is pretty clear and since an E30 will swallow 245/255 rears and 215 or 225 fronts fit and seem to hit the sweet spot I don't really get trying to fit 245s up front personally which is what made me ask the question.

In terms of my statement of too big a tyre not helping, it's additonal rotating weight, unsprung weight, gyroscopic effect and hampers steering feel, made worse by requiring a wider wheel too, all of which are negative effects. They might be worth bearing if they bring with them more grip, however if the larger tyre cannot be brought up to the correct temp all the way across the tread and held there then its all for nothing.

That said, if you've spent the time on smaller tyres and have proven data of them overheating beyond their working temperature range, evenly across their tread (i.e overloaded whilst working correctly) then sure, they're obviously warranted and you are in fact under-tyred at the rear, limited by bodywork.

[330icrazy]

Car manufacturers design cars to understeer it is safer than oversteer. That is why you will see A larger tire on the rear of rwd cars.

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[iansane]

General trend of all RWD performance cars in recent history, from every BMW M car, Lotus, small volume track cars, every example of a RWD performance car uses wider rears than fronts. I'm not suggesting not maximising rears (I've got 245s to on on mine) but I simply cant see the need for wedging that same tyre size under the front.


Lotus Elise cup 260 862kg 250bhp 205/46 16 front 235/40 17 rear
Lotus Europa S 995kg 225bhp 195/47 17 front 235/40 18 rear
Lotus Evora 1248kg 280bhp 225/40 18 front 255/35 19 rear
BMW 1M 1495kg 340bhp 245/35 19 front 265/35 19 rear
KTM Xbow 790 kg 300bhp 205/40 17 front 235/40 18 rear
Ariel Atom 621kg ~300bhp 195/50 15 front and 225/45 16 rear
986 Cayman 1295kg 300bhp 225/40 18 front and 265/35 18

I could carry on, but the generall trend is pretty clear and since an E30 will swallow 245/255 rears and 215 or 225 fronts fit and seem to hit the sweet spot I don't really get trying to fit 245s up front personally which is what made me ask the question.

In terms of my statement of too big a tyre not helping, it's additonal rotating weight, unsprung weight, gyroscopic effect and hampers steering feel, made worse by requiring a wider wheel too, all of which are negative effects. They might be worth bearing if they bring with them more grip, however if the larger tyre cannot be brought up to the correct temp all the way across the tread and held there then its all for nothing.

That said, if you've spent the time on smaller tyres and have proven data of them overheating beyond their working temperature range, evenly across their tread (i.e overloaded whilst working correctly) then sure, they're obviously warranted and you are in fact under-tyred at the rear, limited by bodywork.

Correlation /= causation. Just because you see some other cars with small front tires, doesn't mean that is the best equipment they can perform with. Half of the ones listed don't meet your 1100kg weight stipulation and 6 of the 7 don't even share the same drivetrain layout. A rear engine or mid engine car are going to need a much larger tire in the back than a front engine car.

Coincidentally, the one front engine car in your list has over double the horsepower with a comparatively huge tire in the back. I'd wager the designers of the 1m were a bit more restricted by steering feel, fenderwell packaging and overall pricepoint than maximum tire temperature.

All of the weight and bulk of a bigger tire and wheel combo are detrimental but at least in my opinion (and we know how little that's worth!), the extra grip is worth the trade off. It's hard to pass up more mechanical grip if it's so easy to attain.

May I ask that you post your wheel fitment details? I get 235/40/17 et25 under there with a fender roll and no spacers, but it's really close to rubbing on the struts up front and inside on the rears. Car is lowered.

I run 255/40-17 with 17x9 wheels. I can't remember the offset off the top of my head but I can check on that next time I have the wheels off. I ran 245/45-16s with some super low offset wheel that required flares before so when I went up to 17s I just thought I'd fill them out as best I could. I prefer a square setup since it's primarily a street car.