Thursday, August 13, 2009 - 12:10 pm, by: Dave Cazes(Cazman)
IF YOUR TOO LAZY TO READ, JUST LOOK AT THE PICTURES, AFTER THAT IF YOUR INTRIGUED THEN READ ON.
Just like the front end you cant lower your car too much with all non airbag soarers. There are some slight differences to the front end though.
The wheel/tyre itself has infinite travel in the rear, you can slam it as much as you like without having the tyre smash into body work (not including the outer wheel arch) Where as the front end the tyre hits the upper guard and chops up your wiring loom.
So why cant I lower it too much then?
Simply your shock runs out of travel. The lower you go the less travel you can use. I have provided the measurements on how much travel you have for a given ride height. I have included some pictures if you need the graphical image. This is called BOTTOMING OUT. You might not even notice it, but if you were take a drive in 2 identical cars, but one that doesn’t bottom out and one that does, youd notice. You may think yours isnt, as most of my customers do. They all think “no mine doesn’t do that” but your simply wrong. Refer to the pictures and data below and youll see you are probably riding on the bumpstops right now, you just don’t know it.
The best thing about this problem is there are solutions, unlike the front end.
Now most people will say “but I can get short stroke shocks blah blah” Sorry your wrong. Even if you could buy a short stroke shock, it wont help you. They will only give you less droop travel and wont gain you and bump travel. The other thing is, they simply arent available for our cars. No one makes them, don’t argue. You also don’t need a short stroke shock as I just outlined.
What you actually need is a short “body” shock. The yellow part on my bilstiens would be shorter if they were a short body. One problem, once again they DON’T exist. Sorry to bear the bad news. No brands out there offer a short body shock absorber for our models.
So what can I do to restore my travel issue? Unfortunately you have to change to a coilover in most cases, read on…. Unlike the front, using a short body/stroke COILOVER in the rear actually works. It fixes all you bump problems, but it doesn’t allow you enough droop travel in most cases (or not ideal droop I should say) Many brands out there make a short body coilover, almost any double adjustable height coilvoer will do this for you. Tein superstreets DO NOT, as they are a single adj version.
What is the solution…… This is the easiest and cheapest solution to the problem is what is called in the industry a raised upper shock absorber mount. What this does is mounts the top of the shock shaft inside the boot area rather than level with the top of the shock mount. These work by allowing the shock absorber body to continue travelling up past the body, beyond where it would normally “bottom out”.
With this design you can basically set your ride up to have factory travel at any ride height. In the pictures of mine, even at the rim tucking ride height it is possible to have plenty of suspension travel. This means your car will still ride extremely well.
There is a catch though…. This only works a small amount if you are using lowered springs. There is a limit to how much you can raise the upper shock mount if your using normal springs. The more you raise the mount the more your springs are compressed. 20mm is acceptable in most people’s cases, as almost every lowering spring is 20mm shorter than a stock spring anyway.
Now for the good news…. If your using a coilover setup like myself, OR if you’ve bought some tein super streers (or almost any other coilover) then you can gain back up to 80mm of travel. That’s more than youd EVER need.
The idea is to pick your desired ride height, work out how much Droop VS Bump travel you require and then raise the top shock mount up from there. A good start is to look at the data I have collected, and work out how much droop vs bump your after.
You may not realsie is at the moment, but you may be running a droop/bump ratio of 90/10 at the moment, or 80/20 if your tyre is roughly level with the wheel arch. You can work it out with the supplied data, and if your running any shock absorber, regardless of brand (KYB. Boge, OEM, tociko, bilstien etc) this data is accurate to your case.
This is all I have time for, feel free to ask any questions
Ben Lipman Goo Roo NSW Soarer TT manual, plus TT track car