Help needed on tire size with 18x8 fronts?
03-03-2008, 10:03 PM
#1
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Help needed on tire size with 18x8 fronts?
I purchased a set of take off's from a base carrera that I used for two track events and need to replace the front rubber. I discussed with a couple people on what size tire is best for an 18X8 and have had mixed comments and would like to get more feed back on this.
Current size is 235/40's. Some say on the 8" wide wheel that the 225's is the best fitments. Most manufactures specs say that the 235 and both 245's will work on the 8" wheel. I would like to get the greatest contact patch I can. What are the pro's/ cons going with the 235 or 245?
Current size is 235/40's. Some say on the 8" wide wheel that the 225's is the best fitments. Most manufactures specs say that the 235 and both 245's will work on the 8" wheel. I would like to get the greatest contact patch I can. What are the pro's/ cons going with the 235 or 245?
Last edited by gab997; 03-03-2008 at 10:38 PM.
03-03-2008, 11:12 PM
#2
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I've also read recommendations for the 8" rim anywhere from 225 to 245. Initially I used 235s on 8" rims on a RSA, but then went back to 225, which I stuck with. Porsche has 235/40/18 as the OEM size on the 8X18 Cayman S rims. 245s will fit, but I wonder if they'll actually provide more contact patch than 235s. With at least 8.5" rims, I'd say 245s for sure, but with 8" rims, I just don't know.
Hopefully damon at Tire Rack will see your post and offer his opinion.
Hopefully damon at Tire Rack will see your post and offer his opinion.
03-04-2008, 04:02 PM
#3
Former Vendor
Porsche used and 18 x 8/11 for the 996 widebody with a 225 front. The 997 steps up to a 235 on an 8" wide as well. 245 will fit the OE wheel fine, but may not offer significant benefits over a 235 in performance. In many cases the specs will show a .3" - 1" difference in tread width between the 235 and 245. I know 245 is very tight on the 996, and on the 997 it will probably be as well. If the car is lowered and you are turning hard, you may get some rubbing.
Bottom line, the 245 is likely to be between .5 and an inch wider at the ground, but may rub if pushed over hard enough, particularly if used on an aftermarket wheels with lower offsets.
Bottom line, the 245 is likely to be between .5 and an inch wider at the ground, but may rub if pushed over hard enough, particularly if used on an aftermarket wheels with lower offsets.
03-04-2008, 04:58 PM
#4
I say stuff as much as you can in there.. 245s! Will help dial out some understeer. That said, what are we really talking about here.. 225/235/245. Ideally only 20mm difference from a 225 to a 245. That's less than 1". What size is the rear rubber for comparison (balance). Sometimes it comes down to what size does brand "X" offer that makes the decision for you.
03-05-2008, 12:17 AM
#5
I say stuff as much as you can in there.. 245s! Will help dial out some understeer. That said, what are we really talking about here.. 225/235/245. Ideally only 20mm difference from a 225 to a 245. That's less than 1". What size is the rear rubber for comparison (balance). Sometimes it comes down to what size does brand "X" offer that makes the decision for you.
but, going with a 235 or 245 up front should help with the understeer correct??? Anyone have any luck with this mod in a 993? Thanks...
03-05-2008, 05:03 PM
#6
Yes.. C4s seems to understeer a bit more than C2s do. Going to a wider front tire will help combat this. Also consider your driving style. It could be that a slower in - fast out technique will help you and your car more than overdriving it, as you mentioned may have happened. I don't know your skill level/run group experience, but one thing I love about 911s is rotating the car by lifting off the throttle. When my 911SC would understeer more than desired, a quick lift and then re-planting off the throttle was often enough to transfer weight and get me back "on line" as intended.
I would think the C4 guys (964/993/996) guys have figured out ways to reduce this irritation. Might want to check those areas for ideas too.
I would think the C4 guys (964/993/996) guys have figured out ways to reduce this irritation. Might want to check those areas for ideas too.
03-05-2008, 09:52 PM
#7
Yes.. C4s seems to understeer a bit more than C2s do. Going to a wider front tire will help combat this. Also consider your driving style. It could be that a slower in - fast out technique will help you and your car more than overdriving it, as you mentioned may have happened. I don't know your skill level/run group experience, but one thing I love about 911s is rotating the car by lifting off the throttle. When my 911SC would understeer more than desired, a quick lift and then re-planting off the throttle was often enough to transfer weight and get me back "on line" as intended.
I would think the C4 guys (964/993/996) guys have figured out ways to reduce this irritation. Might want to check those areas for ideas too.
I would think the C4 guys (964/993/996) guys have figured out ways to reduce this irritation. Might want to check those areas for ideas too.
Thanks for the response.
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03-11-2008, 11:27 AM
#8
I purchased a set of take off's from a base carrera that I used for two track events and need to replace the front rubber. I discussed with a couple people on what size tire is best for an 18X8 and have had mixed comments and would like to get more feed back on this.
Current size is 235/40's. Some say on the 8" wide wheel that the 225's is the best fitments. Most manufactures specs say that the 235 and both 245's will work on the 8" wheel. I would like to get the greatest contact patch I can. What are the pro's/ cons going with the 235 or 245?
Current size is 235/40's. Some say on the 8" wide wheel that the 225's is the best fitments. Most manufactures specs say that the 235 and both 245's will work on the 8" wheel. I would like to get the greatest contact patch I can. What are the pro's/ cons going with the 235 or 245?
all tires have a manufacturers spec range for wheel width, a wheel at the wide end of spec will perform better on track than one at the narrow end.
contact patch size will be relatively invariant across the 225-245 size range but contact patch shape, which is the important factor will change. Contact patch shape determines the slip angles that the tire will run at, lower slip angles means lower temps and higher grip.
there are different species of each size in 18, 225/40 & 225/35, 235/40 & 235/35, 245/40 & 235/35, there are also 45 & 50 series for some of these sizes.
another constraint is the need to match the front tire height to the rear within a relatively small %, because of ABS and stability control.
So you have to balance overall height, wheel width spec, tread width and aspect ratio to come up w/ the best compromise for your chassis and use.
03-15-2008, 12:31 AM
#9
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Jungleboy,
I have run 245/35 fronts on stock 18x8 twists on my 993 C4S with good success. The biggest issue is that you may need to find a new tire shop each time you put on a new set of tires if they recognize you! I run Kumho V710 R-comps and they are apparently a real bear to get on the rims unless the rubber is well-warmed ahead of time. Or at least the last two shops who've done mine have had trouble with them seating properly. I rarely see understeer (285/30 at the rear) unless I'm being stupid and going into a slow corner too fast. No setup is going to help you there...
Paul
I have run 245/35 fronts on stock 18x8 twists on my 993 C4S with good success. The biggest issue is that you may need to find a new tire shop each time you put on a new set of tires if they recognize you! I run Kumho V710 R-comps and they are apparently a real bear to get on the rims unless the rubber is well-warmed ahead of time. Or at least the last two shops who've done mine have had trouble with them seating properly. I rarely see understeer (285/30 at the rear) unless I'm being stupid and going into a slow corner too fast. No setup is going to help you there...
Paul
03-23-2008, 07:50 PM
#10
Jungleboy,
I have run 245/35 fronts on stock 18x8 twists on my 993 C4S with good success. The biggest issue is that you may need to find a new tire shop each time you put on a new set of tires if they recognize you! I run Kumho V710 R-comps and they are apparently a real bear to get on the rims unless the rubber is well-warmed ahead of time. Or at least the last two shops who've done mine have had trouble with them seating properly. I rarely see understeer (285/30 at the rear) unless I'm being stupid and going into a slow corner too fast. No setup is going to help you there...
Paul
I have run 245/35 fronts on stock 18x8 twists on my 993 C4S with good success. The biggest issue is that you may need to find a new tire shop each time you put on a new set of tires if they recognize you! I run Kumho V710 R-comps and they are apparently a real bear to get on the rims unless the rubber is well-warmed ahead of time. Or at least the last two shops who've done mine have had trouble with them seating properly. I rarely see understeer (285/30 at the rear) unless I'm being stupid and going into a slow corner too fast. No setup is going to help you there...
Paul
Arun
