Tyre Fight! (Toyo v. Dunlop)

[Koul]

Re: Tyre Fight! (Toyo v. Dunlop)

Hi,

I have had a set of T1-R's on my car for 15,000 miles - the front still have 7/8mm of tread on them and the rears have 5mm of tread left.

They wont last as long as the Bridgestone B340's originally fitted (which lasted me 30,000 miles) but are a much better overall tyre (in my opinion) for wet and dry grip, ride comfort and noise

These are what I will be looking to upgrade to soon but I'm intrigued by Bus_ter's comments about fitting 195/45/16's on the front.

Will these help agility because they will be lighter? Slightly wider spacers than those I have on already will increase the track to restore some of the grip so this is an interesting option.
I'd keep the 205/45/16's on the back.

[miami gulf]

Re: Tyre Fight! (Toyo v. Dunlop)

http://www.camskill.co.uk/products.php?plid=m4b93s103p0

Are these any good to you - the compay do seem to have most sizes - not sure about fitting though

[digi-roadster]

Re: Tyre Fight! (Toyo v. Dunlop)

These are what I will be looking to upgrade to soon but I'm intrigued by Bus_ter's comments about fitting 195/45/16's on the front.

Will these help agility because they will be lighter? Slightly wider spacers than those I have on already will increase the track to restore some of the grip so this is an interesting option.
I'd keep the 205/45/16's on the back.

I think Buster raises a very good point - the spikelines are:

Fronts - 6.5 x 16
Rears - 7 x 16

and you have 205/45's all round.

i am looking at replacing my rears at the moment because I don't want to run the car with tyre tread below 5mm. So, I have been looking at alternative sizes.

After seeing the side profile photo of my car which is in the On-Smart gallery I could clearly see how different the rear tyres look compared to the front in profile even though they are the same tyre (205/45's like yours) - so, intrigued by this I measured the width of my Digi-tec alloys and found this:

Fronts - 7.5 x 16's

Rears - 8.5 x 16's

This explains the visual difference and, using the Tyre Bible's calculator it appears that the rears are right on the limit of acceptability.

So, to answer the question as to why Smart have put 205/45's all round the simple answer is because it was cheaper and easier for them to do so

So, this is where it can get more complex - with your front wheels being 6.5 wide they can take

215/50's
205/50's,
195/50's,
185/50's

but apparently 205/45's don't have enough sidewall height to give optimum ride and handling - but as Buster says it depends on which site you look at - one of the sites I use for tyre calculations says the 205/45's will fit a 6.5 wide wheel

for 45 section tyres you could run:

145/45's
155/45's
165/45's
175/45's
185/45's
195/45's

OK - thats easy enough in itself but changing from what you have at the moment will result in a change of rolling radius. Using the above sizes:

145/45's - 9.16% less diameter difference
155/45's - 7.61% less diameter difference
165/45's - 6.11% less diameter difference
175/45's - 4.56% less diameter difference
185/45's - 3.06% less diameter difference
195/45's - 1.55% less diameter difference

and with the 50 profile tyres:

215/50's - 4.91% larger diameter difference
205/50's - 3.37% larger diameter difference
195/50's - 1.74% larger diameter difference
185/50's - 0.09% larger diameter difference

So, bearing the diameter difference in mind the most suitable front tyre for the 6.5 wide wheel is the 185/50 if you want to retain the 205/45's on the rear as all the guides say they are appropriate for the wheel width and are almost exactly the same diameter.

There is also less rubber and steel so less weight (which is a good thing!)

I realize this has probably confused you more than helped ops:

[Koul]

Re: Tyre Fight! (Toyo v. Dunlop)

I realize this has probably confused you more than helped ops:

Jonathan - I think my brain hurts .

[bus_ter]

Re: Tyre Fight! (Toyo v. Dunlop)

It can become quite complicated

It's interesting to see you're running 205/45's on 8.5' wheels and we're running them on our 6.5' front wheels. That's a full 2 inch difference in rim sizes with the exact same tyre!

You can tell the difference by comparing your wheel photo's with what the spikelines look like. On my spikelines the tyres bulge over the rims (especially at the front). This gives the rims some protection, but I still prefer the way your tyres look as they tightly wrap round the wheels. The tighter tyres must also improve your handling, as oversized tyres distort and flex under faster cornering.

I don't see any reason in changing my 205's for another identical set at the front, they're just unnecessarily big for 6.5' rims. 195's will be a better fit (and cheaper to buy). The 205's will still be fine for the rear wheels, however I'm considering going 195's all round. This way I keep the front and back the same, which keeps the contact patch the same at both ends and also allows for tyre rotations.

[digi-roadster]

Re: Tyre Fight! (Toyo v. Dunlop)

It can become quite complicated

It's interesting to see you're running 205/45's on 8.5' wheels and we're running them on our 6.5' front wheels. That's a full 2 inch difference in rim sizes with the exact same tyre!

You can tell the difference by comparing your wheel photo's with what the spikelines look like. On my spikelines the tyres bulge over the rims (especially at the front). This gives the rims some protection, but I still prefer the way your tyres look as they tightly wrap round the wheels. The tighter tyres must also improve your handling, as oversized tyres distort and flex under faster cornering.

I don't see any reason in changing my 205's for another identical set at the front, they're just unnecessarily big for 6.5' rims. 195's will be a better fit (and cheaper to buy). The 205's will still be fine for the rear wheels, however I'm considering going 195's all round. This way I keep the front and back the same, which keeps the contact patch the same at both ends and also allows for tyre rotations.

Yeah it is a complicated issue

It does seem to be illogical for Smart to provide different sized wheels for the front and rears and then clad them with the same sized rubber

Most front wheel drive cars (including the latest generation of hot hatches) have the same sized wheels front and back clad with the same sized tyres.

Most rear drive performance orientated cars have different sized front and rear wheels. Two very recent examples are the Porsche 911 GT3 and the Audi R8. Their wheel and tyre combinations are:

Porsche 911 GT3

Front wheels - 8.5 x 19
front tyres - 235/35 ZR19s

Rear wheels - 12 x 19
Rear tyres - 305/30 ZR19s

Audi R8

Front wheels - 8.5 x 18
front tyres - 235/45 ZR18s

Rear wheels - 10.5 x 18
Rear tyres - 285/35 ZR18s

Ok - granted these are cars that deliver much more performance than the roadster but I think the comparison is still valid.

It can be seen that there is a larger difference in width between the front and rear wheels on these cars than ours but they are increasing tyre width by about 20mm per inch of wheel width.

Therefore as our cars are provided with wheels that are an inch wider at the back then our rear tyres should be 20mm or so wider than the fronts for an optimum combination of grip, balance and handling.

yes, you are right that oversized tyres will distort and flex under cornering forces which is why it is important to stick within the guidelines offered by these wheel/tyre size calculators. the other thing to consider here is that performance tyres (such as Toyo T1-Rs) have reinforced sidewalls to help minimize this effect.

Having the tyres tightly wrap round the wheel (like my rears) may improve handling slightly but they also have the downside of giving a harsher ride as the sidewalls are stretched across the width of the wheel and they cannot absorb bumps as well

The tyre bible has a very interesting article about the size of contact patches - basically the contact patch of any tyre is the same if it is inflated to the same pressure and has the same static load (the cars weight) applied to it. What changes is the shape of the contact patch - the wider the tyre the wider the contact patch is - as the overall contact patch size has to stay the same so the wider tyre has a narrower contact area front-to-back.

You then start to get into the area of grip and load transfer - which is even more complex

Phew - I think I will lie down now :beerme:

[bus_ter]

Re: Tyre Fight! (Toyo v. Dunlop)

I've just thought of a reason why Smart might put the same size tyres on front and rear.

If one wheel is a slightly different size than the other then it will be rotating at a different rate. Isn't this how the ESP functions?!

AFAIK the ESP knows you've lost traction when one wheel spins at a different speed, so won't the ESP get confused? Possibly turn itself off?

[smarty mad!!!]

Re: Tyre Fight! (Toyo v. Dunlop)

hi back again. i had a look at the sizes of my tyres today: The fronts are 205/40/17 but the backs are 225/35/17. what size tyres could i use for my back rims!? 5mm less on the back!! if i increased to say a 225/40/17 would these tyres fit and would they be cheaper!? help!?

Why not consider Bridgstone tyres i had them on a few cars that i have owned and have been the best tyres. unfortuantly Bridgstone dont seem to do tyres for my car! :silvertri

[digi-roadster]

Re: Tyre Fight! (Toyo v. Dunlop)

I've just thought of a reason why Smart might put the same size tyres on front and rear.

If one wheel is a slightly different size than the other then it will be rotating at a different rate. Isn't this how the ESP functions?!

AFAIK the ESP knows you've lost traction when one wheel spins at a different speed, so won't the ESP get confused? Possibly turn itself off?

Yes I would agree if the wheels are rotating at significantly different speeds - the tyre calculator sites advise to not vary by more than 3% of the diameter of the existing wheel/tyre combination.

I am thinking of 225/40's on my rears whilst retaining the 205/45's on the front - these vary in overall diameter by only 0.78% so I don't see why this difference would cause ESP issues.

If you have 205/45's on the rear and swap the fronts for 195/45's they will run 1.55% fast - if you change them for higher profile ones - 195/50's then they will run 1.74% slow - thats why i think the guide of 20mm tyre width increase per 1 inch wheel width difference is a better starting point so you could change the fronts for 195/45's and the rears for 215/40's which are within 0.5% of each others overall diameter whilst still being very close to the original wheel/tyre diameter.

[digi-roadster]

Re: Tyre Fight! (Toyo v. Dunlop)

hi back again. i had a look at the sizes of my tyres today: The fronts are 205/40/17 but the backs are 225/35/17. what size tyres could i use for my back rims!? 5mm less on the back!! if i increased to say a 225/40/17 would these tyres fit and would they be cheaper!? help!?

Hi,

I taked it you are running on standard Brabus MonoBlock V1's?

If so the rear wheels are 8 inches wide.

Why do you want to increase the height of the tyre sidewall? this will increase the overall diameter of the rear wheels including tyres by 3.66% therefore making your cars gearing longer by the same amount and therefore slower acceleration.

I also don't think you will get them any cheaper because there is more rubber and steel in the 225/40/17's than the 225/35/17's although it may be a more common size?

215/40/17's are going to be 2.4% too slow - you could run 205/40/17's (only 1.07% larger) but why mess with the existing set up which has 20mm wider rear tyres on a 1 inch wider rear wheel which, if you read the previous posts, seem to be in line with the majority of RWD performance cars.

I hope this helps

[Stéphane]

Re: Tyre Fight! (Toyo v. Dunlop)

Just ordered a set of Kumho KU15s semi's 205/50-15 for my trackline wheels:


It's a group buy with a serious discount (20-30%).

[bus_ter]

Re: Tyre Fight! (Toyo v. Dunlop)

you could change the fronts for 195/45's and the rears for 215/40's which are within 0.5% of each others overall diameter whilst still being very close to the original wheel/tyre diameter.

This looks like a good idea However do you think having the rears 20mm wider than the fronts will increase understeer signifcantly? This is a concern as the car tends to understeer anyway, and that's with the tyres the same size!

I need to research into ESP and find out just how sensitive it is to wheel size variations. As Maddan pointed out in another thread it can't be that critical as treadwear will vary the rolling circumference slightly.

[madDan]

Re: Tyre Fight! (Toyo v. Dunlop)

Just try tyres with better grip characteristics than the ones it wears at the momemt, that will probably negate any understeer concerns you have.

I have never noticed any understeer the roady trackday last year showed that to others also, (I had wider rears then also)

[digi-roadster]

Re: Tyre Fight! (Toyo v. Dunlop)

This looks like a good idea However do you think having the rears 20mm wider than the fronts will increase understeer signifcantly? This is a concern as the car tends to understeer anyway, and that's with the tyres the same size!

I need to research into ESP and find out just how sensitive it is to wheel size variations. As Maddan pointed out in another thread it can't be that critical as treadwear will vary the rolling circumference slightly.

Hi,

Am I correct in thinking you are running the "infamous" Bridgestone B340's?

I must say I have never had any issues with understeer

The Brabus roadster also has a larger rear wheel/tyre set-up.

[bus_ter]

Re: Tyre Fight! (Toyo v. Dunlop)

Hi,

Am I correct in thinking you are running the "infamous" Bridgestone B340's?

Yep! Been on the car since new (21K). They've still got plenty of tread left, but they're starting to show fine cracks on the surface. Which means it's time to replace.

I'm still not sure what size tyres to buy! I keep reading through these threads and can't decide 100% what sizes to go for :frown: