Alignment Question - Suspension Gurus
Nov 8, 2016, 07:32 AM
#1
Alignment Question - Suspension Gurus
Saw something interesting on the sandbox yesterday, but didn't get a clear answer for mcstrut cars like ours:
traditional thought is that camber won't impact tire wear as long as you're not running any toe. However:
- M. Daddio
TLDR; you actually should add a tiny amount of toe out for the camber you add on your car for the best (smallest) tire wear
Is that true for mcstruts like ours as well??
traditional thought is that camber won't impact tire wear as long as you're not running any toe. However:
I think what is being missed here is that as you add negative camber, you actually need to add some toe out to negate the camber thrust forces that are working against each other. I run -3 degrees on the front of my vette and couple that with 1/16-1/8 inch of toe out to get the best wear results. I drove my car to 1300 miles each way to Nationals with no major inside wear. It will show after 8000 to 10000 street miles though. Each front tire when cambered produces a vector force towards the other side of the car. if both sides are cambered, these forces fight each other going straight down the road. This is the reason why negative camber at the front makes the car change directions so quickly. The pushing together forces that cancel each other manifest in tire scrub if the tires are pointing straight ahead. For every car and camber combination, there is an amount of toe out that will minimize the scrub of the tire. You can use coast down testing, or do like I did and just run 3/32 toe out for 3 degrees negative. I have a much bigger wear issue on the inside rear on my vette running 1.6 negative with 0 toe than at the front. Hope that makes sense.
TLDR; you actually should add a tiny amount of toe out for the camber you add on your car for the best (smallest) tire wear
Is that true for mcstruts like ours as well??
Nov 9, 2016, 08:38 AM
#3
Between my WRX and Evo, both struts in the front (where all the negative camber is), I can only say I have had good results with zero toe. I can't speak to the geometry aspect, just that's what I've seen. I had a set of RE11s as street tires on the Evo for 4 years that were still going strong when I got a puncture in one of them. I'm guessing 10-12k on them and the inner wear was acceptable considering -3.5 camber in the front.
Nov 9, 2016, 08:29 PM
#5
Makes sense to me. McPherson should be no different than any other suspension.
Land Rover has been using front toe out on the full time 4WD truck chassis for a long time even with live front axle.
FWIW, on my Evo I am running 2.5 degree front camber with 1/16" toe out up front and 1.25 rear camber with 0 toe out in the rear on AD08R's and this has given me the best tire wear yet. Absolutely even wear across the tread for fast road use on both front and rear.
Didn't like toe-out in the front initially on my old tires where the inside had already worn - on those 0 toe felt better.
It also is consistent with the built in toe change in the suspension as the front suspension will increase negative toe on compression, whereas the rear will increase positive toe on compression.
PSRS, spherical rear trailing arm bushings, rear bump steer bsuhing and front steering precision kit button things down for better toe control and tire wear as well. For motorsport I would probably up the camber from 2.5 in the front ....
Land Rover has been using front toe out on the full time 4WD truck chassis for a long time even with live front axle.
FWIW, on my Evo I am running 2.5 degree front camber with 1/16" toe out up front and 1.25 rear camber with 0 toe out in the rear on AD08R's and this has given me the best tire wear yet. Absolutely even wear across the tread for fast road use on both front and rear.
Didn't like toe-out in the front initially on my old tires where the inside had already worn - on those 0 toe felt better.
It also is consistent with the built in toe change in the suspension as the front suspension will increase negative toe on compression, whereas the rear will increase positive toe on compression.
PSRS, spherical rear trailing arm bushings, rear bump steer bsuhing and front steering precision kit button things down for better toe control and tire wear as well. For motorsport I would probably up the camber from 2.5 in the front ....
Nov 9, 2016, 08:43 PM
#6
so the camber on the front passenger's tire for example, sets the vector to point slightly left - and then you set the toe out to "straighten" that vector?
i get that that will straighten the vector, if i'm understanding it correctly, but what i dont get is, the vector may be straight but any amount of toe is still going to change the direction of the vector vs the direction of the tire rotation isn't it?
i get that that will straighten the vector, if i'm understanding it correctly, but what i dont get is, the vector may be straight but any amount of toe is still going to change the direction of the vector vs the direction of the tire rotation isn't it?
Nov 10, 2016, 08:09 AM
#7
I recently read on a different enthusiast forum that some front toe-out can help with outside shoulder wear.
Does this make any sense at all? I asked the writer if he could explain but did not get any follow up posts from him.
I have been running -2 degrees camber with 0 toe up front for the past 2 years (SCCA B-Street) on my X. The outside shoulders on my front tires are absolutely getting murdered with the inner half still looking brand new. Since I can't add any more camber without moving up a class I am open to trying anything that can possibly alleviate the shoulder wear.
Does this make any sense at all? I asked the writer if he could explain but did not get any follow up posts from him.
I have been running -2 degrees camber with 0 toe up front for the past 2 years (SCCA B-Street) on my X. The outside shoulders on my front tires are absolutely getting murdered with the inner half still looking brand new. Since I can't add any more camber without moving up a class I am open to trying anything that can possibly alleviate the shoulder wear.
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Nov 10, 2016, 08:18 AM
#9
I hate to hijack the thread, but could you explain why? I'd love to have less outside shoulder wear even at the expense of some additional inner wear (feel free to PM me instead of replying if you don't want the thread going off topic).
Nov 10, 2016, 08:55 AM
#12
that's exactly what i thought. daddio is saying the opposite for his vette at least, so i was at the least wondering if it's geometry related, or if it applies to all cars. maybe if you're wearing the outside of your tires really badly, with toe out you can wear the insides badly as well, lol? but then he would have said even wear, as opposed to better wear
Nov 10, 2016, 09:15 AM
#13
EvoM Guru
iTrader: (1)
Same here.
that's exactly what i thought. daddio is saying the opposite for his vette at least, so i was at the least wondering if it's geometry related, or if it applies to all cars. maybe if you're wearing the outside of your tires really badly, with toe out you can wear the insides badly as well, lol? but then he would have said even wear, as opposed to better wear
