Hi Ryan, no problem at all. We are pleased you are enjoying the articles.

Thanks

Hi Ryan, thanks for the comment. Our guide is designed to work for all makes, models and styles of coilover so there is a degree of generalization that leaves room for you to tweak the instructions to your specific needs.

With regards to the bump stop, they come in different sizes and can be small or large. Therefore we advise removing it so you can measure the full range of the damper. Also it is worth noting that the bump stop is not solid. Therefore when it has the mass of a corner of a cornering car compressing it through a fast section over kerbs, the bump stop will compress. Therefore we set the ratio without it so that we never actually exceed the full range of the bump compression as that would cause the damper to lock out and stop working completely which is a bad situation to come across out on track.

Therefore, your 1 inch bump stop could quite easily compress to half that or less when it is actually used therefore, you are still using up the ratio. This does also depend on what material your bump stop is made from. So if you have a particularity stiff bump stop then you might want to leave that on and include it in your measurements.

Thanks

If I measure the damper shaft travel total (bumpstop removed) and leave 2/3 of it for “bump” travel by adjusting accordingly and 1/3 of it for droop……..Doesn’t putting the bumpstop back in place then naturally interfere with that available 2/3 travel?

Say I have a 3” stroke (Bumpstop removed) and I leave 2” for bump and 1” for droop, but then I put my 1” physical bumpstop back in place. Does that not leave me with only 1” of travel before hitting the bumpstop and 2” of droop?

Thanks,
Ryan

Hi Justin, thanks for the comment. IN the vast majority of cases, coilovers tend to be assembled and packaged without too much in depth measurement due to people setting the coilovers to their own ride height preferences upon receipt. Therefore we always advise setting the ratio yourself.

You can always speak to your coilover manufacturer and ask what their recommended specific bump/droop ratio would be for each set. If they have a designed figure then you can use their values instead of the rule of thumb of 2/3rd to 1/3rd and still carry out the procedure. It is also always worth double checking that they are definitely set to the designed ratio if they have one.

Thanks

Hi Ron, thanks for the comment.

This is covered within the article towards the end. We mention that once you have set the damper ratio, you install the spring and let the car sit on the spring. At this point you use the spring base adjustment to raise the car back to the designed ride height which will set the bump/droop ration back to the correct position. This is because unless an extremely stiff spring rate is being used the cad will always compress the spring when loaded, altering the bump/droop ratio that was set with Kirk a spring. Therefore you use the spring base adjustment as a final point of adjustment to ensure that you have the correct chassis ride height and bump/droop ratio with the spring installed.

The spring will be compressed in this process but the spring rate will not be altered in doing so so there is no concern to handling by doing this.

Thanks

I have some questions about determining the spring length in order to optimize its length to the damper travel length, in conjunction with setting the damper position for 2/3 bump | 1/3 droop. First, an example scenario: The damper has a travel length of 210mm, which would mean I would want to set the damper position for a bump length of 140mm and a droop length of 70mm.

Next, the vehicle has a corner weight of 300kg. Assume a motion ratio of 1.0, to make it easier to calculate.

If I choose a 5kg/mm spring rate (to suit the ride frequency of the axle), when applying 300kg as the static corner weight, the spring will compress 60mm.

So now, if the spring is compressed 60mm, at static corner weight, there will be another 80mm of bump length available. And from static position, there will be 130mm of droop available.

Assuming this is correct, how do I now determine the correct spring length, for the given linear rate spring and damper travel, in order to maximize the suspension travel?

Also, if the difference between the unloaded and fully compressed spring length of the spring is less than the full bump length of the damper, how does that affect the chosen spring length?

Thanks!

Hi Alex, the top mount can be left on and the bump stop can be left on if there is still shaft showing once fully compressed. If not then remove the bump stop. You are looking for the different in exposed shaft between fully open and fully closed so you c an measure to any known point on the shaft as long as it is still showing on full compression and full open. Removing the bump stop for measurement depends upon your particular coilover and whether it leaves shaft showing or not which is too specific to include in the article unfortunately.

You can leave the top mount on for the whole process as it can all be done with the shock mounted and bolted to the car too.

We have altered the article now to remove any confusion with regards to bump stops.

Thanks

When measuring the exposed shock tube are you removing the top mount and the bump stop? Are you measuring from the very top of the exposed threads?

When compressing the shock is it the same, without top hat / bump stop? Do you have any diagrams to show this?

Also in your article you say to set the vehicle ride height and then jack the wheel up to the bump stop but in the next section say to reinstall the spring and bump stop?

Many thanks

Hi Cark, thanks for your comment. Preload (with a linear rate spring isntalled) does not really exist. For example, if you applied 300kg of “preload” to a spring and then sat 100kg onto the spring, it would still compress again by the amount determined by the spring rate. When you are adjusting ride height using the spring plaftorm and it begins compressing the spring on full droop, it will not affect the spring rate at all unless it is compressed so much that the coils bind and become inactive. Therefore, it does not matter if your springs are compressed by different amounts when corner weighting as each spring will still respond the same weight identical spring rates.

This does change if you have variable rate springs installed which change in spring rate as it compresses but this is a much rarer application.