What caster with Howard Coleman setup

[Gunnytron]

Just curious to know if anyone has got their setup with the Howard Coleman specs.

What caster did you end up with?

I want to ensure my setup is in the right ball park.

 

[shaunwil]

Maybe a better question on Rx7club ? Not sure too many people would have that info.

 

[4packet]

A single alignment spec is pointless, it has to consider the specific car setup/spec as well as the application (how/where you drive it) and how you want it to feel. Acceptable tyre wear is also a consideration. My front tyres will judder through a corner with less than about 1.7 degree camber. The rear is not stable without a bit of toe in. Ideally I would run more rear camber on track, but the tyre wear on the inside edge would be tedious on the road.

If you read the full thread you will see there is some chatter about caster which makes sense. Caster gains you camber in a corner and self centres the steering. Drivers sometimes don't like the feel of it.

I also think Howard's posts should be taken with a pinch of salt. His spring rates would be best suited to a farm track, not a race track and 1.2 degrees camber might be OK for a trip to the shops. I run zero front toe and have never noticed a stability issue. A lot of non-RX7 track cars run toe out to help then turn in (my Caterham for example).

 

[Gunnytron]

A single alignment spec is pointless, it has to consider the specific car setup/spec as well as the application (how/where you drive it) and how you want it to feel. Acceptable tyre wear is also a consideration. My front tyres will judder through a corner with less than about 1.7 degree camber. The rear is not stable without a bit of toe in. Ideally I would run more rear camber on track, but the tyre wear on the inside edge would be tedious on the road.

If you read the full thread you will see there is some chatter about caster which makes sense. Caster gains you camber in a corner and self centres the steering. Drivers sometimes don't like the feel of it.

I also think Howard's posts should be taken with a pinch of salt. His spring rates would be best suited to a farm track, not a race track and 1.2 degrees camber might be OK for a trip to the shops. I run zero front toe and have never noticed a stability issue. A lot of non-RX7 track cars run toe out to help then turn in (my Caterham for example).

I always value your input as you seam to know your stuff.

What you say is no doubt true, however, I have to start somewhere. Are you basing your experiences mainly with track driving? Mine will mainly be street.

 

[4packet]

Mine is based on a compromise between road and track. Tyre type and size is probably your biggest factor in alignment. Wider, lower profile tyres are less tolerant of aggressive settings. I'm on 235/255 17s. Howard suggests he is running 255/295 18s. The stiffer your suspension bushes are, the closer you can run to the ideal alignment (parallel toe for example). Alignment print outs also give a false sense of accuracy. Measure the same car 10 times, you would likely get 10 different results.

I think mine has around 7degrees of caster. If setting up purely for road, I would probably go 1.2degrees camber depending on how hard you drive. Maybe consider running a little more on the front vs the rear. I would likely still aim for zero front toe with just a small amount of toe in on the rear. The important thing is how it drives and how the tyres wear, rather than getting too hung up on the numbers. Toe is easy to adjust directionally until you are happy for instance. Just mark a position and rotate 1/4 turn on each side.

Definitely paint mark all your alignment settings. That way you can see if anything has moved (Samberg subframe is notorious), or been dismantled and can then return to roughly the right position or increase/decrease from a known starting position. It's not too hard to measure the basics yourself. String line for toe and camber with a weighted line measuring the distance top and bottom of the wheel rim. Trigonometry can then calculate the camber. The tricky bit is getting the car on the level as garages floors are rarely flat. I use a laser level to shim the car to a level point.

 

[Gunnytron]

Good info, ta. I am currently running 225/45/17x8 front, and 255/40/17x8.5 rear on my stock wheels.

When I finish my split rims I will probably be running 255/40/17x9 front, and 255/40/17x9.5 rear.

When you are levelling, where on the car are you setting the laser level?

 

[4packet]

I use the lowest point of the wheel rim from the inside. The laser from the front of the car hits all 4 wheels.

This might give you some inspiration. I use slightly larger drain pipe from Screwfix for the toe. I bought the B&G strings, but fishing line tied to a socket works fine. The challenge on a closed wheel car is making adjustments without disturbing the strings. It's quite easy on the Caterham.

 

[Gunnytron]

Nice, thanks!