Tire temps versus alignment settings

[old guy]

There is a recent thread discussing various settings for a lowered suspension set up. Clicky click. I probably should have posted there but I would like to get another thread started and open for discussion.

I just got back from a 80 mile drive on the Interstate. Tire pressures were 40psi (cold). Average driving speed was just under 75 mph. As soon as I got home I checked the surface temperatures across all four tires. Results as follows:

FRONT
Fender to ground height 25-¼"
Camber at -1°15' (factory range -0°22' to -1°12')
Toe set to 0°00' (factory range 0°05' to 0°15')

Inner edge of both tires 139-142°. Center of tire 128-125°. Outer edge 125°

REAR
Fender to ground height 25-¼"
Camber set to -1°00' (factory setting)
Toe set to 0°10' (factory setting)

Inner edge of both tires 123-126°. Center of tire 125-120°. Outer edge 120°.


Has anyone else recorded tire temperature gradients side to side? Sure would be nice to have a few more reference points. As you can see from the results above the front tires showed a 15° gradient whereas the rears only showed a 6° gradient. Do I need to dial in more or less toe in the front? Based on the data above it looks like a little more toe performs better. Intuitively I would guess just the opposite. However I don't know if it is reasonable to compare differences between the front and rear of the car.

Discuss?

[evo_ski]

I wish I had some equipment to measure tire temp so I could add to this thread as this is pretty much exactly what I was aiming to find in my post. Hopefully some other people are able to chime in.

[alpinevr]

Would the extra weight of the motor on the front tires increase temp by a little? I like where this is going though.

[Snooter]

Excellent question old guy. I'd very much like to see where this goes as I'm going to be in need of an alignment soon and have been debating about what to have the front toe set at. I will borrow a friend's laser temp gun this weekend and report back.

[Bische]

Good topic OG, i know EBG 18T has done temp measures.

Im sure he will chime in

[EBG 18T]

Good topic OG, i know EBG 18T has done temp measures.

Im sure he will chime in

Haha..

Yeah I used a digital pyrometer to dial in the tire pressure. I always run the same alignment with 0 toe.

[old guy]

Ok: Since the time I started this thread I have replaced all four tires and both front wheel bearings. I had the alignment set just prior to the original temperature readings. I repeated the same drive today. The ambient air temp today was 72°f. I believe it was in the upper 80's when I took the initial set of readings. I suspect that I need to have the alignment checked after dismantling the front suspension to replace both front wheel bearings. I took three readings on each tire. Temps are listed as read across the tires from drivers side to riders side.

LF 103 104 108____________117 112 102 RF



LR 98 103 105____________110 106 105 RR


It just so happens that my wife got home at the same time I did after a similar drive on the Interstate so I also took a reading on her tires. The CC has the exact same tire as the A4 (235/40/18 Conti DWS) except hers have about 20k miles on them.

LF 100 100 105____________100 98 99 RF

LR 92 98 100____________95 97 93 RR


Observations: Inner edge of all tires on both cars are running hotter than the outer edges. Apparently something is seriously out of whack with my front right wheel alignment. Even though I didn't disturb the tie rod length I'm guessing that the alignment changed a little from removing everything to replace the wheel bearing. As you can see there is a 15° gradient across that tire whereas all the others on both cars are in the 5° to 7° range. It will be interesting to see what's different on the front right. Time to head back to the alignment rack. Hopefully the new information will give me a better idea as to whether the toe or the camber is the cause. My homemade toe checker indicates a very slight amount of static toe in but I have no way of determining if it is coming from the left side or the right side (or a combination of both). I'll post the results once I figure it out.

Cheers!

[Charles.waite]

My homemade toe checker

Thats awesome. What did you make? some sort of cardboard stencil with degree markers?

[old guy]

Thats awesome. What did you make? some sort of cardboard stencil with degree markers?

A homemade version of this: All you really need are two straight sections of anything (2'x4', angle iron, etc) with 2 slots cut in the ends.

[old guy]

Another update for anyone that is interested:

I went ahead and adjusted the toe to zero assuming the right side was the offending party. I was able to get back to 0° toe but ended up with the steering wheel being slightly offset to the left when going in a straight line. When I got home after a 400 mile trip I measured the tire temps and they all fell within a 5-7° gradient across the face so I knew I was on to something. I reversed the adjustment out of the right side and split the adjustment equally between the right and left side. The steering wheel is now dead on center. Yesterday I ran a 540 mile round trip and checked the temps at the end of both 270 mile runs. Temps were still in the 5° to 7° range across the face. The only thing I didn't like was that the car seemed to wander very slightly left/right and required frequent slight steering adjustments. Nothing radical. I had my cohort drive a little to get his impressions and he said that he only noticed it because I had pointed it out.

The next step I plan to do is to introduce about 3' of toe per side to see if it adds to the "on center" feel without raising the inner edge tire temps.

We shall see!

[EBG 18T]

You will be able to fix the 'wander' with adding a tad positve toe. But you may need to adjust your tire psi to offset the temp change. If your inner is still 5-7perfect higher temp try pulling 1.5-2 psi out of the offending tires.

[old guy]

You will be able to fix the 'wander' with adding a tad positive toe. But you may need to adjust your tire psi to offset the temp change. If your inner is still 5-7perfect higher temp try pulling 1.5-2 psi out of the offending tires.

Thanks for the tip Eric! I set all 4 tires at 36 psi before I left yesterday (the ambient was in the upper 40's) but I neglected to check them at the end of each 270 mile run. I'll post up whether or not 3 minutes of toe is enough to make a difference in the "on center" feel and if it changes the temperature gradient at all.

[Charles.waite]

Do you use something like this to measure the temps:
http://www.amazon.com/HDE-Temperatur.../dp/B002YE3FS4

I need a new toy...

My house's insulation blows so I could use it to pinpoint cold spots in the house as well...

[old guy]

I use this: Clicy click. a really nice multipurpose tool. It has a built in IR scanner with a laser pointer to pinpoint the spot you are reading. Plus it has every electrical reading and monitoring function you could ever need. Google the model number (81079) and you can find one for a decent price. They run ~$110 at Sears.

[Charles.waite]

Nice! Two things I need! The only problem its much cheaper to buy both as separate devices than to get the all-in-one. Thanks for the idea though OG.

[old guy]

Thanks for the tip Eric! I set all 4 tires at 36 psi before I left yesterday (the ambient was in the upper 40's) but I neglected to check them at the end of each 270 mile run. I'll post up whether or not 3 minutes of toe is enough to make a difference in the "on center" feel and if it changes the temperature gradient at all.

Here's what I know so far: I'm currently running 4.5 minutes' of toe per side. On-center feel is perfect. I am continuing to monitor the tread temperature gradients and so far the variation has been no more than 8°f across the face of the tire. Tactile feel across the tread indicates no feathering or scalloping. Will continue to update as the mileage increases on this set of tires.

[onlyaudis]

been using this method to double check on my alignments and tire pressures for years. used to actually have access to a "tire Pyrometer" that i borrowed form a race car friend of mine. I use a IR thermometer now as well. JC Whitney used to sell an inexpensive but very accurate toe gauge I use, and I got an electronic camber gauge I picked up years ago that works well. doing (and at least checking) alignments with "track side" equipment works great because you can drive the car and re-measure to confirm the car has settled. it also allows you to play around like "old guy" did in this post, and find the magic setting for your car and driving style.

tire pyrometer



I also often find too much air is in the tires for optimal setting, and this shows up as higher temps in the center of the tire. Many people set the cars up with too much air in the tires. this can make the car feel more responsive,(its like you have narrower tires) even though you are actually losing traction and wearing the tires uneven.


it is still a good idea to have a 4 wheel "computer" alignment done after a major front end parts swap/ coil over install,for a starting point. Of course, you need to find a place that knows what they are doing and will set the car to the specs you want.

this looks like an upgraded better version of the toe gauge I have

http://www.ebay.com/itm/Race-Toe-Gau...r#ht_500wt_969

[diagnosticator]

You will be able to fix the 'wander' with adding a tad positve toe. But you may need to adjust your tire psi to offset the temp change. If your inner is still 5-7perfect higher temp try pulling 1.5-2 psi out of the offending tires.

Positive toe is toe out. Negative toe is toe in. I read somewhere that a pos or neg toe of 1/8" on a 16" tire, effectively scrubs the tire sideways about 30 feet per mile traveled.

[EBG 18T]

. I read somewhere that a pos or neg toe of 1/8" on a 16" tire, effectively scrubs the tire sideways about 30 feet per mile traveled.

That wouldn't suprized me. It is amazing what an 1/8th can do.

[Charles.waite]

Resurrecting this.

Old Guy, do you think these alignment specs you've worked out would work as effectively on a non-sport suspension?

I'm wanting to get my B7 an alignment before a long road trip (Seattle to Whitefish, MT) and when I rotated the tires a month back there was a bit of outer edge wear. Tracking and handling are great, but I'm concerned that the outer edge wear might destroy the tires prematurely.

I mean I don't see why it wouldn't work with the non-sport suspension, but I could be overlooking something.

I was thinking of having them set the stock specs at the rear, and 4.5 minutes of toe up front. Thoughts? Modifications to my proposed specs?

[old guy]

That’s pretty much what I have settled on. I just measured and rotated my tires Saturday and the wear is pretty uniform across three of the four tires. The inner edge of my right front is showing about 1/32” more wear than the rest of the other three tires. Don’t really know why at this point. Maybe because of the increased road crown on the right side?

I don’t see why it wouldn’t work for the stock suspension either. The factory toe settings seem to be more for stability than tire wear. A setting of 0° toe should give the best wear. Adding a very slight amount of toe-in seems to help with the stability. You may have a problem getting the shop to provide 0° toe. Most of the newer alignment racks require the technician to pull up the factory settings and then they adjust from there. So if the factory setting is 5’-15’ of toe the tech is going to set it to the “0” point which will actually be 10’ of toe. If he gets it dead nuts on “0” the printout will then show that the toe is set at 10’ per side.

If you can get him to actually set it to ~4’ of toe per side that would be good. If not, you can have him adjust it to the factory center of 10’ of toe per side and then adjust it back yourself to whatever you want.

[Charles.waite]

Thanks. The places I've spoken to font mind me giving them specific specs for the toe so I'm guessing they'd be able to compensate or at least alter the "zero point".

Good info as always though Fletcher. I'll be sure to reports back with how the car handles. Won't have a pyrometer, but I'll do my best "back if the hand" measurements after the 10 hour drive.