# 235/40-18 on an '08 GTI?



## rs_hunter (Nov 9, 2008)

I've been thinking about converting my GTI's OE 17x7 wheels to winter duties, using a set of 215/50-17 performance winter tires. For the rest of the year I'm considering the 235/40-18 size, on a set of 18x8 wheels. The offsets of the wheels I'm considering are all over the place at 40, 42, 45, 48 and 55. I want to avoid rubbing as much as possible, and maintain wheel travel and turning angle. The suspension is currently stock. Any advice as to what offsets will work, and what to avoid?
TIA








EDIT: To clarify that I am seeking advice on appropriate offset range.


_Modified by rs_hunter at 11:02 AM 2-7-2009_


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## orionz06 (Jun 15, 2005)

*Re: 235/40-18 on an '08 GTI? (rs_hunter)*

225/40/18 is oem 18" size


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## rs_hunter (Nov 9, 2008)

*Re: 235/40-18 on an '08 GTI? (orionz06)*

Yeah, I know, but the OE 18" is a 7.5 wheel and I'm not sure about the offset. 
Plus, all vehicle speedometers are off by X% and the minor increase in overall diameter would only serve to reduce the error. With the shyte roads around these parts a bit more sidewall wouldn't hurt any either and would help reduce the visual effect of the fender gap. The 215/50-17 and 235/40-18 combos are also about as close to exact matches as one can get. The 215 section tire is also a better match for the OE 7" rim width.
I'd also like to be in a position to drop the car a bit without having to deal with a hassle I could have prevented by better positioning the wheel at this point.










_Modified by rs_hunter at 10:49 AM 2-7-2009_


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## onequickg60 (Dec 3, 2000)

*Re: 235/40-18 on an '08 GTI? (rs_hunter)*

235 is also factory on some rims i have to factory take off pirelli tire from a GTI.. either size will do on a 8 inch rim..


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## rs_hunter (Nov 9, 2008)

*Re: 235/40-18 on an '08 GTI? (onequickg60)*

Any idea what would be the best range for offset with a section width of approximately 9.8"? Thanks


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## rs_hunter (Nov 9, 2008)

Just for giggles, I'll throw out this idea...
How about the possibility of something along the lines of a 255/35-18 on a 9" wheel? Section width would be 10.3". The key is that I don't want to be screwing around with the bodywork...
Could it fit? What sort of offset would I need?


_Modified by rs_hunter at 12:11 PM 2-7-2009_


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## orionz06 (Jun 15, 2005)

*Re: (rs_hunter)*

why do you want a taller tire? the 225 should work up to 8.5" wide... too wide of a tire might rub...


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## rs_hunter (Nov 9, 2008)

*Re: (orionz06)*

I'd like to put more tread width on the pavement for better grip. The sidewall height difference (from the OE 225/40-18 to a 235/40-18) is very little, going from 90mm to 94mm. That's an increase of only 0.15748 inch.


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## orionz06 (Jun 15, 2005)

*Re: (rs_hunter)*

i doubt you will notice the footprint difference... youre better off to stick with the correct size and a common size should you damage a tire and need it replaced asap... and that aside, going to a better tire in the OEM size will be better for grip than going to a tire that has a different footprint (that isnt much larger)


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## JDriver1.8t (May 20, 2005)

*Re: (orionz06)*

Your stock offset is 45 IIRC. You will want to stay as close to this as possible, or down to about 35 using spacers.
A 235/40/18 will fit with zero problems. They come on some of the cars, and audi's on the same platform.


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## rs_hunter (Nov 9, 2008)

*Re: (orionz06)*

I've already checked and there are quite a few choices in the 235/40-18 size. Just a quick check at TireRack showed 51 options in the top three summer tire categories, with a "V" rating or better, compared to a whopping 53 in the OE size. Most of the models are common to both tire sizes.
Checking the spec sheets on the tires I'm considering, the tread width increase is ~.5 inch on average. That's a better than 6% increase in actual tread on the pavement, not just section width.
I guess I should have mentioned that I deal with tires quite a bit as I own a truck fleet. Dealing with tire numbers isn't something foreign to me, as hard numbers in tire specifications are an absolute requirement in the transport industry. It's the tire/wheel positioning in the wheel housings of a GTI that I'm not sure about.
Thanks


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## rs_hunter (Nov 9, 2008)

*Re: (JDriver1.8t)*

Thanks, that's what I was looking for. Just how close should I stay to that +45 offset? Is it better to stay at +45 or below by a few, or can I safely go up a few as well? I think I'd rather avoid spacers.
Cheers


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## orionz06 (Jun 15, 2005)

*Re: (rs_hunter)*


_Quote, originally posted by *rs_hunter* »_I've already checked and there are quite a few choices in the 235/40-18 size. Just a quick check at TireRack showed 51 options in the top three summer tire categories, with a "V" rating or better, compared to a whopping 53 in the OE size. Most of the models are common to both tire sizes.
Checking the spec sheets on the tires I'm considering, the tread width increase is ~.5 inch on average. That's a better than 6% increase in actual tread on the pavement, not just section width.
I guess I should have mentioned that I deal with tires quite a bit as I own a truck fleet. Dealing with tire numbers isn't something foreign to me, as hard numbers in tire specifications are an absolute requirement in the transport industry. It's the tire/wheel positioning in the wheel housings of a GTI that I'm not sure about.
Thanks










i was refering to obtaining a replacement locally... tirerack is great when you dont need the car an a few hours... 

the tread width, based on the tire size itself is going to be 10mm wider... or 0.39"... the shoulder treatments of tires today will also change the actual footprint, so the change could be reduced even more...
the footprint size will be elliptical, so i dont believe it will work out to a simple area of a rectangular area calc...
all that being said, for the sake of filling the wheel wells a tad more, i have been toying with the same size on my R32... my concern came when no one had tires in stock within 20 miles...


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## rs_hunter (Nov 9, 2008)

*Re: (orionz06)*

Ah, I get where you're coming from...
I have a number of major suppliers, within a reasonable distance, which can supply a replacement either later the same day or the next morning. In any case, I don't see it as a very significant issue, as the size difference is very minor. A simple case of an under-inflated tire would lead to a greater difference in the rolling radius between two tires than the 4mm change from a 225/40 to a 235/40. This makes the size difference with my spare a non-issue. 
Of course this doesn't help in your case, with the R32 not having a spare tire. An inexcusable omission on VW's part, IMHO... BTW, have you considered buying a cheap aftermarket wheel that'll clear your front caliper? You could go with a size that is narrow enough to fit within the spare tire well, yet still match up with a 235/40-18. It'd save potential headaches on a number of fronts.
The ~.5 inch figure I gave is the actual measured tread width. The footprint itself would become a (as viewed from the side) slightly narrower, longer oval, as the vehicle's weight would create essentially the same total footprint area, using a tire with an equal weight rating. All else being equal, the shape would degrade the tires braking and acceleration capacity while increasing it's ability to handle lateral forces.
As I'm going to be replacing a _supposedly_ all-season tire with a top rated summer performance tire, I'm quite confident that the acceleration and braking capabilities will far exceed anything the current pattern has been capable of. I'm more interested in cornering capabilities anyhow, as I'm not into drag racing and I'll jump on my motorcycle when the "leave 'em in the dust" bug bites.


















_Modified by rs_hunter at 3:25 PM 2-8-2009_


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## JDriver1.8t (May 20, 2005)

*Re: (rs_hunter)*

The stock offset is 45mm. If you went 51mm, then I would not go any wider, or would add 10mm spacers to make them et41.
I believe most people run a et38-40 on aftermarket wheels that are 8'' and under. I have seen a few MK5 with 8.5 et35 and they are slightly poking.
I would try to keep final et between 40-45.
That will fit a 235 with no problems.


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## rs_hunter (Nov 9, 2008)

*Re: (JDriver1.8t)*


_Quote, originally posted by *JDriver1.8t* »_The stock offset is 45mm. If you went 51mm, then I would not go any wider, or would add 10mm spacers to make them et41.
I believe most people run a et38-40 on aftermarket wheels that are 8'' and under. I have seen a few MK5 with 8.5 et35 and they are slightly poking.
I would try to keep final et between 40-45.
That will fit a 235 with no problems.

Awesome! Thanks man, you've just made my day.








Now to just make up my mind on which wheel design I'm going to go with. Decisions, decisions...


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## orionz06 (Jun 15, 2005)

*Re: (rs_hunter)*


_Quote, originally posted by *rs_hunter* »_Ah, I get where you're coming from...
I have a number of major suppliers, within a reasonable distance, which can supply a replacement either later the same day or the next morning. In any case, I don't see it as a very significant issue, as the size difference is very minor. A simple case of an under-inflated tire would lead to a greater difference in the rolling radius between two tires than the 4mm change from a 225/40 to a 235/40. This makes the size difference with my spare a non-issue. 
Of course this doesn't help in your case, with the R32 not having a spare tire. An inexcusable omission on VW's part, IMHO... BTW, have you considered buying a cheap aftermarket wheel that'll clear your front caliper? You could go with a size that is narrow enough to fit within the spare tire well, yet still match up with a 235/40-18. It'd save potential headaches on a number of fronts.
The ~.5 inch figure I gave is the actual measured tread width. The footprint itself would become a (as viewed from the side) slightly narrower, longer oval, as the vehicle's weight would create essentially the same total footprint area, using a tire with an equal weight rating. All else being equal, the shape would degrade the tires braking and acceleration capacity while increasing it's ability to handle lateral forces.
As I'm going to be replacing a _supposedly_ all-season tire with a top rated summer performance tire, I'm quite confident that the acceleration and braking capabilities will far exceed anything the current pattern has been capable of. I'm more interested in cornering capabilities anyhow, as I'm not into drag racing and I'll jump on my motorcycle when the "leave 'em in the dust" bug bites.

















_Modified by rs_hunter at 3:25 PM 2-8-2009_

the R has a donut... 

ok, you understand the footpring change as well, and are seeking the lateral forces... most of the time people get a wider tire for "more grip" but dont understand how it really works...


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## rs_hunter (Nov 9, 2008)

*Re: (orionz06)*

I'm glad to see VW finally wised up on the R32, the earlier guys were stuck with a can of Fix-a-Flat.








Cornering is where it's at! I'm lucky to have all kinds of roads, not far from here, that would make a WRC pavement stage proud. Quick, lots of curves and very little traffic. Ah, nirvana...


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