Dialing Back Roadster Understeer

[wiztecy]

Dialing back the Roadster Understeer may be an even more appropriate thread to merge the Camber talk into:
Dialing Back Roadster Understeer

My last alignment with the shims in, the camber came out to be:

Left Front: -0.5
Right Front: -0.7


(Left ABS mounting bracket shim thickness: 3mm)
(Right ABS mounting bracket shim thickness: 1mm)

*A 1mm shim plate affects camber by .25 degrees.

New front Camber (by math) after front ABS shims removed:
Left Front: -1.25
Right Front: -0.95

Now looking at this, I may add the left .25mm shim to the Left front. That way I'll have a -1.0 on the Left front and a -.95 on the right. Or the other possibility is on the next alignment to see if the right front camber can be increased to match the -1.25 Left.

Left Rear: -2.0
Right Rear: -2.2

Also appears Roger Reid did this same process sometime back. It appears that the only shims on the Tesla Roadster are the ABS brackets, so mine appear to have still been factory fresh with no extra shims:

SRRSCCA autocross results 8-14-10 [Archive] - Tesla Motors Club - Enthusiasts & Owners Forum

 

[Doug_G]

Dialing back the Roadster Understeer may be an even more appropriate thread to merge the Camber talk into:
Dialing Back Roadster Understeer

Good suggestion - done.

 

[wiztecy]

I installed the right 1mm (.25 degree) ABS shim bracket to the left, chopped off the ABS mount on it so its just a regular shim since I couldn't hang the ABS wire on it anyways. Looks clean. My front camber in theory should now be close to:

Left Front: -1.00
Right Front: -0.95

As for recommending the shim removal, I like it. But you'll have to try it and drive it to really know. Unless you're feeling the understeer, there's most likely no need to change. As for me, I was getting lots of understeer when driving and pushing hard into 35-40 MPH hair pins and overshooting more than I wanted. I still want to break the rear end hard more with this new configuration in order to put the new feel of the Roadster into my personal memory and reflex coordination if things get a little wild unexpectedly.

 

[strider]

rear snap w/ stock non-adjustable shocks? That's what I have and I have to really work to get the rear end try to come around. The front end always pushes . When I was new to the Roadster and had the stock AD07's front and rear I was rushing to make a stale left turn arrow and, not being familiar w/ the Roadster's acceleration, was doing about 50mph as I went over the crosswalk. Front end pushed. I stabbed the brakes and whipped the wheel left and then the rear end came loose. Steered into the slide and made the corner. But the amount of initial understeer shocked me.

I would like a little more front end bite but not overdo it. I want it to be more balanced in it's behavior, like my Corvette. I've been hoping I could just do it with stickier tires but maybe I should just go visit Dietschwerks. Though w/ my pending Mission Motorcycle purchase I'll be pushing the vehicle spending budget for the year.

 

[wiztecy]

Here's some interesting specs if you're running the Yokohama A048 tires:

***When tightening down the Hex bolts after removing the shims, identify what grade hex bolt you have. It will be either an 8.8 grade, tighten them down to 45 Newton Meters (33 foot pounds) or a 10.4 grade that needs to be tightened to 68 Newton Meters (50 foot pounds).
Lotus Elise Shim Removal

The bolt should be stamped on the head, either 8.8 or 10.4 (this is a random bolt pic pulled off the web, not Roadster specific):

 

[wiztecy]

Reporting back with how the Roadster drove with the shims removed. Huge improvement on my daily drive. Some key points:

-Steering wheel feels heavier, my guess is that there's more rubber being planted on the pavement.
-The Roadster use to have a tendency to wander when the front wheels were hitting parallel grooves in the road. Most of that's gone.
-Not getting the plow of understeer like I use to when accelerating or cornering, feels as if the Roadster hugs the Road now.
-Steering is not as twitchy as it use to be. Part of it could have been that my passenger side camber was more aggressive than the driver's side before pulling the shims. But also since more of the tire is planted on the pavement, the car follows a path better.
-Car tracks better without the shims than with them.

When I pull my wheels off for my tire change I'll pull the hex and take a pic/note the hardened grade bolt and list the proper torque setting. I torqued it to the lower number for now, but my feeling is that Tesla put in the higher grade bolt since it was post 2004 production(where Lotus upgraded the bolt). But one only knows by doing a personal verification what it really is.

 

[dhrivnak]

I added shims as I had significant wear on the insides of the tires and the spec called for more neutral camber. I think I went from -3.5 to about -1.5. It sounds as if I went the wrong direction if I were to need the best handling. As it is I prefer the better range on the tires.

 

[wiztecy]

I would like a little more front end bite but not overdo it. I want it to be more balanced in it's behavior, like my Corvette. I've been hoping I could just do it with stickier tires but maybe I should just go visit Dietschwerks. Though w/ my pending Mission Motorcycle purchase I'll be pushing the vehicle spending budget for the year.

Unfortunately with stickier tires it won't be consistent in its behavior. And when/where are you going to heat up the tires so they stick? I've only seen the AD07/08 get sticky when temps were 95 to 100 degrees F (and that's a 180 tread wear compound). And if you're below 70 degrees, good luck unless your pushing and pushing the tires with lots of friction. Even Doug mentioned he had a hard time heating up the A048 tires, and that's softer than the R888's that I hear mixed results with on the street.

The adj. suspension will give you more to work with, that with shims you've got lots of tricks you can do with getting the front end to bite. If you have a 2.x you can put the 235's on the rear to help out, with that I'd run 205's on the front to match the original configuration (Discussed on Lotus Talk). I can't do it since I have a 1.5 and the tire rotation is way out of line.

Cool to hear about the Mission cycle, that'll be fun!!! You'll enjoy it for sure. Let me know when you get it, would love to see that sexy beast.

 

[hcsharp]

I added shims as I had significant wear on the insides of the tires and the spec called for more neutral camber. I think I went from -3.5 to about -1.5. It sounds as if I went the wrong direction if I were to need the best handling. As it is I prefer the better range on the tires.

Where did you get the shims? They're harder to find than they used to be.

 

[hcsharp]

I added shims as I had significant wear on the insides of the tires and the spec called for more neutral camber. I think I went from -3.5 to about -1.5. It sounds as if I went the wrong direction if I were to need the best handling. As it is I prefer the better range on the tires.

Where did you get the shims? They're harder to find than they used to be.

 

[djp]

Where did you get the shims? They're harder to find than they used to be.

I picked up some rear shims from my local Lotus dealer. I needed more than they had in stock, but they were able to ship them in a few days.

 

[dhrivnak]

The service guys were great and gave me 6. I just had to ask. I offered to pay but they just sent them via mail.

 

[wiztecy]

I think I went from -3.5 to about -1.5. It sounds as if I went the wrong direction if I were to need the best handling.

A -3.5? That number sounds really high and would cause some significant wear. I've never heard anyone run such an aggressive camber like that, on the positive side yes with sticker tires, but not in the negative. Did you purposely dial it in like that for super hard tires up front?

I'll definitely monitor my front inside tire wear and adjust if needed.

Sector 111 has a nice set that are in .5 mm thickness (that Lotus doesn't have) but pricey at $99 for a big set:

V2shims

 

[wiztecy]

Update: After a few days driving the Roadster feels very good and balanced. When accelerating hard and making a quick turn I can feel the tires slightly loose traction from the bumpy imperfections in the road and lightness of the front under full accel but it immediately comes back. Also over HWY 17 if feels more planted through turns and not as jumpy in the front.

One thing is that you really have to feel out your own configuration, there are many variables that play into the handling of the vehicle. Alignment specs, suspension settings, swaybars, weight of the driver, etc. So what works for one person may not work at all for another.

 

[dhrivnak]

A -3.5? That number sounds really high and would cause some significant wear. I've never heard anyone run such an aggressive camber like that, on the positive side yes with sticker tires, but not in the negative. Did you purposely dial it in like that for super hard tires up front?

I'll definitely monitor my front inside tire wear and adjust if needed.

Sector 111 has a nice set that are in .5 mm thickness (that Lotus doesn't have) but pricey at $99 for a big set:

V2shims

I agree -3.5 sounds extreme. After watching both my rears and front tires wear noticeably more on the inside I did an alignment the car was way off with a 2 degree toe in and aggressive camber. Not sure if the first owner did this planning to race or if that is how Tesla aligned the early cars or if my alignment shop is off. I figure I will have the answer in 8 months where I can really see the tire wear. If things are not even; then off to find a new alignment shop. I am always nervous when the car is way off of spec.

 

[wiztecy]

I agree -3.5 sounds extreme. After watching both my rears and front tires wear noticeably more on the inside I did an alignment the car was way off with a 2 degree toe in and aggressive camber. Not sure if the first owner did this planning to race or if that is how Tesla aligned the early cars or if my alignment shop is off. I figure I will have the answer in 8 months where I can really see the tire wear. If things are not even; then off to find a new alignment shop. I am always nervous when the car is way off of spec.

I'd like to see if anyone has the "before" specification on their alignment. I went to what I thought was an aggressive -2.0 camber in the rear and this was the 1st alignment my Roadster ever had since it was delivered. Before having the alignment my rear tires were wearing very hard on the inside, like you had mentioned on yours. After going to the -2.0 camber its wearing allot less on the inside (was surprised) as compared from before. The rear tires have a pretty even wear across the whole plane of the tire now. From your observation and mine it appears the -3.5 may have been a Tesla "mistake" thing. It was my understanding Tesla didn't align the Roadsters themselves but had some alignment shop do it. Possibly they were given the wrong numbers. They seem very far off from the Elise specs for sure.

An aggressive negative rear camber by Tesla's spec was to be no more than a -2.0:

http://www.hcsharp.com/tesla/roadsterAlignSpecs/AlignSpecs.htm

 

[hcsharp]

I'd like to see if anyone has the "before" specification on their alignment. ...

This was after I had the car for a year.
Before:
Front Camber: L: -.57 deg; R: -.30 deg
Rear Camber: L: -2.3 deg; R: -2.3 deg

Caster were all normal

Front Toe: 3.5mm Total (ouch!)
Rear Toe: 3.0mm Total

 

[Doug_G]

(Left ABS mounting bracket shim thickness: 3mm)
(Right ABS mounting bracket shim thickness: 1mm)

*A 1mm shim plate affects camber by .25 degrees.

Same as your car - my left bracket is 3 mm, and right bracket is 1 mm. I also had a 1 mm shim on the right side.

Sector 111 has a nice set that are in .5 mm thickness (that Lotus doesn't have) but pricey at $99 for a big set:

V2shims

I picked up one of those sets. I removed the shim from the right side, and replaced the 3 mm bracket with a 2 mm shim on the left side. I cable-tied the ABS connector to the gap where the shims mount.

After some driving with hard cornering I measured the tire temperatures with a pyrometer. It's still warmer on the outside indicating I could put in some more camber.

Subjectively, I would say there was a distinct improvement in handling. A welcome change - quite noticeable but I wouldn't say it was dramatic.

I'll take it to autocross as it is now to see how well it works - I suspect it will be noticeably better. But I'll probably end up going to 0 mm right, 1 mm left.

 

[wiztecy]

Thanks Doug for the update! Looking forward hearing how it feels on the autocross cornering. What pyrometer are you using? Appears the lasers temp readers won't work for tires, only the probe type. Good point understanding where heat is generating to get the best traction then make adjustments from there.

Here's a link discussing more on the pyrometer:
Using a tire pyrometer-949 Racing

 

[Doug_G]

I'm using this: AccuTech Economy Pyrometer


Yes, you need a probe; the surface of the tire cools down too quickly.

After some more driving this weekend, I'm really liking the additional camber. The car feels a lot better when cornering at the limit, and the limit is definitely faster.