rijowysock

have an 11' Cayenne coming end of the month........

so far i ordered the truck on the 18" Cayenne Wheels (10 spoke (18x8+53 on 255/55/18)) and going to have them done Satin Black by the dealer to try and get an appearance like "Cole"



i also bought some 22" HRE (22x9.5+47 on 285/35/22) which will be for daily use i assume.. (not sure yet)




my question stems from this post: HERE
i was going to buy another set of stock 18" Wheels (18x8+53) and place some 265/65/18 BFG AT tires on them (Same as Transsyberia Truck) my question is does anyone have such a large OD tire on their truck? any problems if so? (member above put the 60 series without problem, but another series means another inch)

getting the above for off road use... figured if they chose them for the Transsyberia that they would be the size to get.... also would the TPMS have any problems with such a large OD tire on the vehicle? (stock 29", 265/65 is 31.6")




-Riley

Mike in CA

255/55/18 694 Revs per mile
285/35/22 676 Revs per mile
265/65/18 639 Revs per mile

The 265/65/18's will essentially make your gearing almost 10% taller, which is significant. If those tires were used on the Transsyberia, makes we wonder if they didn't change the rear end or transmission ratios in that truck to compensate.

rijowysock

yeah the math comes out:

22's on 285/35/22 are 2.8% slow, so when speedo says 60 i am going 61.7MPH

the "BIG" transsyberia tires 265/65/18 are 8.7% slow, speedo says 60 im going 65.2MPH

from what i have read from searching the transsyberia's with the 265/65/18 have minimal mods, but the mod's they do have are made to make it handle better offroad... i would assume the transmissions are the same, or is everything modified? i have no problem with a speedo being off (never really use it anyway).. but i do not wish to cause harm to the trans/electronics... i know with AWD gearing is tricky but i am keeping the same size "gears" all around... the change in size would affect torque and horsepower but im curious if it would hinder the vehicle at all, (people on here run 60 series, but why not 65?) i searched up and down and figured id try and settle the debate for myself and others in future.

found a gorgeous pic of a trans:




found them: HERE

good post here by cole: HERE

person asked in the past, but no replies: HERE

another link with varying size info: HERE

rijowysock

also for the record i typed in the other sizes for OEM '11 Cayenne wheels, they fluctuate as well:

265/50.19 1.3% slow
275/40.20 1.3% fast
275/45.20 2.4% slow
295/35/21 0.3% slow

which is how i justified the 285/35.22 (have seen the 295/30 and did not like the look of the tire on the truck)

Mike in CA

I had to go to a couple of different sources, and this is the internet so you can take it with a grain of salt until/unless someone has more definitive info. But according to these links, as I suspected, the Transsyberia has a shorter geared rear axle ratio compared to the normal S to compensate for the taller tires: 4.11 versus 3.55. FWIW.

2009 Transsyberia Spec


2009 Cayenne S spec

rijowysock

sad face on gearing... i guess 60 series is the max then.

bgsntth

I really liked the Yokohama AT-S 265/60-18. They are an H rated all terrain with great dry/wet grip for an AT. Very quiet and a nice ride, comparable to an all-season. Not quite as good off-road as the BFG, but a much better tire on the tarmac - lighter too.

rijowysock

these:



"Yokohama Geolandar A/T-S
Treadwear: 500
Traction: A
Temperature: A
Speed Rating: H



Yokohama Geolandar A/T-S
Product Details

Geolandar A/T-S all-terrain tires have an aggressive design that'll make today's trucks or SUVs stand tall. But the real beauty lies deeper. With features ranging from Multi-Stepped Grooves to Dual Interlocking Pyramid Sipes, every Geolandar A/T-S packs the absolute latest in technology to deliver long, even treadwear. Featuring an extensive size line-up, the Geolandar A/T-S, and its powerful on/off-road performance, can be experienced accross a broad range of applications."

Cole

I'm used to taking Jeeps with 27" stock wheels and upgrading them to 40" meats. So I get a little giggle out of this topic.

Th Cayenne has enough gears in the box (8 on the 2011) that you are really not going to have much of an issue with gearing.

If you look at this chart you can see what I mean. The goal of a ale gear change is to keep the engine within its efficient operating range. Or, in the case of the Transsyberia race rig to put it up higher in the rev range and developed more torque.

Th stock tire sizes are all about 29" tall. The large Transsyberia size is about 31.5" tall. (just google metric tire conversion and you can find these yourself if you like, the chart below we developed for big rubber sizes in inches)

The chart shows the acceptable range of rpm for most motors running down the highway in their 1:1 gear. (not overdrive). Lower in the rpm range but within the limit is considered good for fuel mileage. Higher in the range but within the limit is considered for "more power".

You can see with 3:55 axle gears moving from the 29" to 31" tire just lowers your rpm slightly but keeps it within the range. (even more so on a 6-8 speed gearbox). You can also see where the Transsyberia rig is actually just higher in the range with 4:11 axle gears. (probably stolen from a V6 Cayenne if you really want a set). Keep in mind this rig was set up to RACE!

Cole

I'm going to make this a second post since I'm posting from my iPad.

For full disclosure you should realize that the ABS and PSM will be "slightly" effected by this change since they use wheel speed as part of their calculations. Since you will be traveling slightly further per tire rotation than the computer thinks you are it will slightly slow the response from the ABS and PSM. Probably not enough for you to notice it honestly.

We did a lot of testing with this on a closed course with some modified Jeeps with ABS and stability programs. A well tuned butt and back to back runs on a course and you can feel the difference. (and these were bike 35" to 40" tired Jeeps) Like I said, probably not noticeable with such a small change on the Cayenne.

bgsntth

Yes, that is the Yoko that I was referring too. FWIW, it has a 30.5" diameter.

rijowysock

EDIT: Found: HERE 3.7 final drive ratio on 8speed auto for 2011
the V6 either manual or 8SP says 3.7, the V8 says 3.09 HERE

so:
Manual 2011 3.7
Auto 2011 v6 3.7
Auto 2011 v8 3.09

so black is good, yellow is more tq, blue is more mpg?.. so the stock 2011 v6 is good and 31.5's would hurt less than on a v8 with 3.55 ?