I know this has been asked before, but is there any definitive answer to how far i should cut my bumpstops down by? i will be fitting -40mm koni springs to strandard dampers.
when I fitted springs to my std corsa shocks years ago the instructions in box said to cut them in half. Whether that was specific to the car/springs I don't know. was 10years ago now...
I think bump stop cutting is supposed to be dodgy? How about proper shorter ones from Powerflex or similar?
what would be dodgy about it? lol have you ever seen a lowered car with the bump stops still the original length? seen the way that when the car is sat on the ground the bump stop is in contact with the lower half of the strut? recon driving a car that is suspended by the bump stop would be un-dodgy? if you lower by 40mm, cut out at least 40mm of bump stop. its just logical
I didn't mean to say it was good to leave a car sitting on them , just in one of the books on chassis tuning I'm sure it said it was better to replace them with proper short ones rather than cut ones.
if you cut a bump dtop by 40mm i doubt if there will be anything left worth putting on the car . look around for some uprated ones mate .
i think if you are using standard length shocks, leave the bumpstops alone. it doesnt matter how far you lower a car, the bumpstops are there to prevent the shock piston hitting the base of the shock under excessive load, e.g. if you drive too fast over a speedbump. cutting them with standard shocks will just mean that you will damage your shocks straight away! unless of course, vw design their bumpstops too long, and there is a safe amount you can cut off? if you are using shorter dampers, i guess you can cut that amount off the bump stop (e.g. if your dampers were 40mm shorter, cut 40mm off the bumpstop). if you are running on the bumpstop normally, you should be using shorter shocks or coilovers lol
I recall Golden once saying that the rear bumpstops form part of the spring rate. They fill the gap between the spring plate and damper body completely. If they are worn, or falling apart, then the rear end does not have the required spring rate. I'd imagine that if you are using OE bumpstops on a lowered setup, that you'd need to cut the bumpstops accordingly - as they'd be too long - but without leaving any gaps.
how about doing it mathematically. say your spring has 10 coils at 10 mm thickness i.e. fully compressed length of 100mm then if you measure that length onto the shocker and see how much travel is left. as the bump stop is supposed to stop spring fully compressing leave bump stop a bit longer than this . do you get what im trying to say?.
You cut off the amount that you are lowering by - particuarly important at the back as the BS's also act as a 'spring assistor' and if you don't cut them then the car will be riding on them... GSF do febi rear bump stops which are rubber rather than foam so don't disintegrate like the VAG ones - just use a hacksaw to cut bottoms off... For the fronts you can either cut the originals if the foam is ok or fit the shorter mk4 ones.
same here... had two mk3 with lowered suspension kits, both used original bump stops and top mounts without any problems. When fitting there was sufficient clearance between bump stop and strut housing, ~2inches of travel before any compression. haha.. on the other hand, my tyres would be rubbing like mad long before that amount of travel.
when i got my mk3, the rear appeared to be a touch lowered, but probably due to old spring. the ride was attrocious, there was all of 5mm travel in the rear suspension. i thought the dampers had seized. when i had a look, with the car on the ground the bump stop was basically resting on the body of the damper, hence no suspension travel. i cut it back and it was fine after that, the ride was actually good
wouldn't that suggest that the length of the bumpstop is the entire shock travel length, if that is the case I would say your shocks are wrong. I have 40mm lowered koni t/a's on my mk2, if anything the bugpack poly bumpstops are exactly the same length just without the dust cover (that will come off eventually and rattle around the bottom of the spring!) most sensible answer here is about the length of your strut (standard vs shorter). you surely should only ever see the use of your bump stop on maximum travel and they are there as a precautionary measure.
Yeah, I got some of these from GSF when I lowered the Vento, they are rubber and stiffer than the original foam ones. I cut them down by what I thought was the appropriate amount (about 40mm, according to the drop I was getting from the springs, and using shortened dampers), but the car still rode on them and felt absolutely horrible. There was a tiny amount of suspension travel and it would bounce hard. Hence why I disagree with the idea that they are an integral part of the suspension in normal operation. Since then I cut them down some more and the ride is much improved. They are still long enough to prevent the dampers from bottoming out and to deal with heavy load in the rear - which I have had on numerous occasions.
