Tyre size differences ?

[ClassiChimi]

Could anyone confirm if a
245/40/17 rear tyre has a higher side wall than a
225/45/17 the 45 on the 225 suggests it's higher but I beg to differ,, is it a percentage of the tyre width,,
Can anyone lead me to a chart that I can check how these numbers are calculated. Cheers Al

[simonwedge]

Al

Here you go: http://www.willtheyfit.com/

[ianwayne]

I like this site too. Gives a visual perspective:

http://www.kouki.co.uk/utilities/visual-tyre-size-...

And if you're thinking of changing wheels, this one is good to check offsets:

http://www.1010tires.com/Tools/Wheel-Offset-Calcul...

[Richard 858]

^+1 to all above. Yes Alun, the profile figure (40, 45 etc.) is the height of the side wall calculated as a percentage of the tyre width.

[QBee]

....so 245/40, the sidewall in millimetres is 245 x 40% = 98mm
and 225/45 the sidewall in mm is 225 x 45% = 101mm

So in theory the 225 has the higher sidewall, by 3mm.

But the question comes down to "are both tyres worn by the same amount?". With new tyres having 8mm of tread and knackered tyres having 2mm, a half worn 225/45 will be exactly the same sidewall height as a brand new 245/40.

In other words, don't get hung up on a 3mm difference.


Just to confuse you further, if the 245's a Toyo track tyre (R1R or R888R) and the 225 is a road tyre, the 245 will be bigger because Toyo make their track tyres bigger than other manufacturers' road tyres (most make them smaller than advertised)

[SILICONEKID345HP]

My personal opinion regarding the 245/40/17`s look so lost in the arch .


I`ve moved on to 235/45 17 which look a lot better and have a better feel due to the extra wall height .


I will never go back to the 245`s. These tryes grip like hell ,I can`t even get them to spin in the wet .


http://www.camskill.co.uk/m54b0s312p111650/Uniroya...

Edited by SILICONEKID345HP on Sunday 7th February 11:35

[MPO]

SILICONEKID345HP said:

My personal opinion regarding the 245/40/17`s look so lost in the arch .


I`ve moved on to 235/45 17 which look a lot better and have a better feel due to the extra wall height .


I will never go back to the 245`s. These tryes grip like hell ,I can`t even get them to spin in the wet .


http://www.camskill.co.uk/m54b0s312p111650/Uniroya...

Edited by SILICONEKID345HP on Sunday 7th February 11:35

Any idea on the difference in total weight, i'm looking at reducing total wheel/tyre weight at the moment...

MPO

[ClassiChimi]

Thanks guys, ive got it Sussed,,
As you say Anthony my bald old tyres are rather smaller than when they started out in life,, the Toyo's do seem more chunkie but their also on different rims so hard to tell really, I'll pull them off and line them up against the old Avons,,

Going by what I've got I would lik 245/45/17 and 215/45/17 to fill the Arch better and be a bit more compliant but the 40's in the Toyo are pretty spot on really.
I used to fret over the wheels filling the arch more but recently it doesn't concern me and as I'm running the car at a fairly high ride height it makes no odds. These new wheels I have are offset slightly more than my old wheels and that sort of makes them look more aggressive anyway,
I have to say the Toyo's suit the car far better than my old Avons,,although having such crap tyres was a huge buzz in a way, I'd long since worked out the braking distances and such with them,, the rears were so hard I could spin wheels on command upto about 90 mph,, felt like I had 400 hp,,, it's now faster but more planted,, I need more power

[QBee]

Alun, you do need to match your tyre widths to your wheel widths. So, for example, a 245 tyre will need a wheel between 8J and 9.5J.

See this chart to understand what is possible

tyre width chart

[ClassiChimi]

yeah I've got that Anthony,, be interesting to see mine up,against Rich's car with the SP12' with a 20 mm off set. About the same track as the ones I'm now running by the looks of it,,, nice and wide

Edited to add, I'm sure mine are a 30 mm offset front and rears but my minds been elsewhere recently, I'll mail Andy who I got them from and check. I'm having the wheels off again to balance and play about with geo this week so I'll actually take a closer look at them.
The car handles better and less role,, I've also sriffenef up the shocks as the tyres offer better compliance, 22 psi all round,, nice

Edited by ClassiChimi on Sunday 7th February 14:54

[QBee]

Am assuming that you are going through a Bolshoi phase, and "sriffenef" is Russian for make harder?

[Richard 858]

QBee said:

Alun, you do need to match your tyre widths to your wheel widths. So, for example, a 245 tyre will need a wheel between 8J and 9.5J.

See this chart to understand what is possible

tyre width chart

Alun, just to complicate this further the tyre width to wheel rim width relationship also varies depending on wall height / profile as the lower the profile the less the tyre will "stretch" over the rim restricting the suitable tyre width further and conversely the greater the profile the greater the suitable width that can be accommodated.

[seeby]

QBee said:

Am assuming that you are going through a Bolshoi phase, and "sriffenef" is Russian for make harder?

I just love your sarcarsticness Anthony.

[ClassiChimi]

Yep, I've got that Richard, My Bolshie period maybe

[ChilliWhizz]

SILICONEKID345HP said:

I can`t even get them to spin in the wet .

That's coz you've only got a meagre 345HP

[SILICONEKID345HP]

ChilliWhizz said:

That's coz you've only got a meagre 345HP

Yes but more torque than you and also quicker down the quarter mile

[ChilliWhizz]

SILICONEKID345HP said:

ChilliWhizz said:

That's coz you've only got a meagre 345HP

Yes but more torque than you and also quicker down the quarter mile

That's very true Daz
On a serious note, how are the rainsport's for wear?

[Skyedriver]

There's been quite a few good reviews on this forum for the Rainsport 3. How do they compare with the T1R? I'm thinking roadgoing hillclimb class, with short burst from cold/standstill.

[SILICONEKID345HP]

ChilliWhizz said:

That's very true Daz
On a serious note, how are the rainsport's for wear?

Ive only done around 250 miles .. They are very soft ,probably good for sprints and pod but would probably go a bit wobbly on track days because of the soft side walls.

The car seems to drive better with 205 50 16 fronts rather than 225 45/16

My rears are now 235 45/17.

[QBee]

I have Rainsprout 3s on my daily Saab, and have virtually gone through the front tyres (front wheel drive) in 18,000 miles, most of which are cruising up and down the A1 in queues of traffic, no max power stuff at all. Rears still have 7mm on them.

So in conclusion, the wet grip and dry grip are both awesome, and they should be really good on a road going Chim, the only trade off being a higher wear rate because they are a softer compound tyre.

With the mileage you guys do in your TVRs you might get 15 years out of them if you take it easy.