Trim Your Bump Stop With Lowering Spring?

[Silentnoise713]

Question for folks who are on lowering springs, did you trim your bump stops? I came across a few pics of lowered Mz5s but folks seem to reuse the factory bump stop as is. May be b/c they are integrated into the dust boot, which most prob don’t want to cut. What spring are you running, how low are you, and do you often experience bottoming out? Not for stock shocks but trimming the bump stop will allow more suspension travel on your shocks, which most aftermarket.

I’m happy to see Fat Cat has bump stops for the Mz3 but they are matched to particular shocks .
http://www.fatcatmotorsports.com/FCM_Bilstein_products_MS3.htm
http://www.fatcatmotorsports.com/FCM_Koni_products_MS3.htm



EDIT: FCM ‘did’ recommend different stops for Bilstein vs Knoi shocks but they, being Miata specialties first, did not realized MS3 Bilsteins are inverted (FRONT only) with built-in bump stops, Miata Bilsteins are standard. While you can open them to replace the stops, FCM decided to remove their suggestion for Bilsteins b/c original setup will give you full tavel without exceeding damage point.

 

[DKaz]

I've heard nothing but bad things with the Fat Cats. Just trim the OE bump stops.

 

[Silentnoise713]

ORLLY?! I don't think I've read a negative review but of course I don't read every forum. Fat Cat is highly praised in the Miata world. They have a rep who is very active on the Miata forum and discusses and explains a LOT about the intricacies of suspension and dynamics. I've learned a bit myself. I would like to know what bad things you’ve heard. I plan on getting them when I lower (helps to smooth out a lowered ride) and they are pricey to boot -considering what you get in terms of a physical product.

I've always trimmed OE bump stops when I lower my previous cars but believe there is more improvement (better ride and better damping) with a set of properly matched bump stops.

 

[DKaz]

Ok he found out it was his swaybar bushings not the Fat Cat bump stops. lol. So he takes back his negative review.

 

[flcruising]

I've always trimmed OE bump stops when I lower my previous cars but believe there is more improvement (better ride and better damping) with a set of properly matched bump stops.

You base your ride quality on bump stops? Shocks provide dampening, but I've never heard of investing in a set of bump stops. Those things are only there for the occasional over-compression of your suspension. I didn't realize people relied on them for everyday driving.

 

[Silentnoise713]

You base your ride quality on bump stops? Shocks provide dampening, but I've never heard of investing in a set of bump stops. Those things are only there for the occasional over-compression of your suspension. I didn't realize people relied on them for everyday driving.

Yes and no. I wouldnt say I base ride quality on bump stops alone but a proper set will enhance your overall suspension setup. Long bump stops mean less suspension travel, shorter bump stops allow for more suspension travel. So for OE bump stops, the amount that you trim is the amount of extra suspension travel you get back (if you lower car) which you have to be sure the shock can handle (Koni, Bilstein).

Also, it does not help that bump stops are progressive in design so when you trim off the lower end (top end is designed to fit the shock mount), you are cutting off the softer end and leaving the stiffer end so when you do hit it, youll get a nice jarring bounce. Aftermarket bump stops are designed to be shorter yet still retain some progressive nature and theres also the better material quality to further enhance its effectiveness. I would say the average car does hit the bump stop often like when going over a bump/hump, most movements at highway speeds (unless you drive on a smooth surface) as the forces will pull the car down and there will be less suspension travel.


Would you agree with the following?

All shocks have different compression (bound/rebound) rates?
-This is why it is important to match the proper set of springs with the right pair of shocks (personal preferences dictates as well). Youd have to look up specific shock compression charts to know what you are getting and compare that to the spring rate. This would affect when and how hard your shocks will hit the bump stop. Theres also the point that while progressive springs are more comfortable, they are sifficult to match with shocks b/c shocks are not progressive by design. Linear springs are more appropriate to match with shocks. The better shocks have the options of being revalved to your liking (comfort or aggressive).

All shocks have different effective ranges?
-If you put all of the different Mz5 shocks by different makes side by side, youll see that they are not all the same length. They are all valved differently and some have longer bodies and/or shafts, which leads some to think the aftermarket shock will raise the car. It is safe to assume that if they work differently then they too should have different stopping points.

All shocks will blow if exceeding its range?
-This is where the bump stop comes into play, to prevent excessive compression and also soften the rate very end of the compression. But if you use, for example, unmodified OE bump stops, which tend to be very tall, your shocks will not get to fully compress and work in the range which it was designed for and hit the bump stops too early. It would be great if shock manufacturers provide bump stops with their shocks but I can also image itll be difficult b/c of the various drops offered by various springs manufacturers.


These are my conclusion from what Ive learned from various suspension forum discussions. Some Miata folks are fanatical when it comes to suspension ("It's more fun to drive a slow car fast than a fast car slow). Ive always trimmed OE bump stops myself but for the Mz5, I am considering bump stops b/c I want as much comfort as I can get (for the kids) and still retain a sporty ride (for myself). However, $$ will always be a factor too.

At the moment, I am leaning towards H&R sport springs (progressive), Mz3 Tokico HP (cheaper) or Mz3 Bilstein HD (expensive but had them in the past and absolutely love them), and Fat Cat bump stops (they are listed as for MS3 so I am weary they may be meant for more aggressive use ).

 

[DKaz]

They make Tokicos for Mazda 3s now???

 

[Silentnoise713]

I looked up the thread again and realize they are talking about the MP5!! Arggggg...

The Mz3 has been on the market since '04(?), why does it seem to fall short of aftermarket support?

 

[steronz]

Yes and no. I wouldn’t say I base ride quality on bump stops alone but a proper set will enhance your overall suspension setup. Long bump stops mean less suspension travel, shorter bump stops allow for more suspension travel.
...
Also, it does not help that bump stops are progressive in design so when you trim off the lower end (top end is designed to fit the shock mount), you are cutting off the softer end and leaving the stiffer end so when you do hit it, you’ll get a nice jarring bounce.

Maybe your experience with bump stops is different from mine. There's no comfort about them. They're there to prevent the shock piston from shooting through the bottom of the housing when you drive over a railroad tie, and nothing else.

When you lower a car, you lose suspension travel, true. Generally, stiffer springs are used, which means the car doesn't go lower than it did stock. It starts lower and compresses less, and they end up at the "bottom" somewhere around the same point. On a stock suspension, you should never know that the bump stops exist, unless you find the aforementioned railroad tie in the middle of the road. When you bottom out, a) you've already used up all your suspension travel in a frighteningly short period of time, meaning you and all your passengers are already getting a good jolt, and b) the car comes to an even more abrupt change in direction when it contacts the bump stops, meaning you and all your passengers are now wondering if the transmission is still in the car. There's nothing pleasant about this, and there's no graceful way to contact the bump stops.

Sometimes lowered cars bottom all the time because there's not enough suspension travel. In that case, the idea is to cut the bump stops just to get them the f out of the way. They're still only there to protect the shocks from damage, but at least now you're not hitting them constantly.

If you're bottoming out frequently, either cut your bump stops or change your suspension up. Getting "cushier" bump stops isn't going to make anything more pleasant for your kids.

eta: For what it's worth, I've got the H&R springs and I haven't hit the bump stops yet. I think you'll be fine with the stock ones.

 

[Silentnoise713]

Required reading. Let me know what you think afterwards.
http://www.cardomain.com/ride/742393/1991-mazda-miata-mx-5


Shaikh is the owner and founder (?) of Fat Cat. You can read up on his other posts as well. Discussion is Miata specific but the concept applies to all cars. Major difference being there is no vendor out there focusing this much effort on tuning a Mz5. Luckily, they do offer a product for the MS3, which should apply to the Mz5 with some limitations (weight difference). http://forum.miata.net/vb/showthread.php?t=401320&highlight=bump+stop

The bump stops every single production vehicle I've ever seen has used the bump stops in cornering. This includes Porsches, BMW, etc. They are meant to prevent the suspension from locking solid (causing something to break) primarly in extreme compression via a sharp rise / fall-off in the roadway. But, the factory often will tune the length and density of a bump stop to affect handling. In the case of the NC/RX8, the front stops are firmer than the rear and engage earlier, so you'll essentially get terminal understeer especially with the previously 'standard practice' alignment that recommended more rear camber vs. front. I hope those dark ages are over.

 

[bootman]

You don't need to trim your stops if you use the right shocks with lowered springs to begin with. (ie. Koni yellows)
Never use stock shocks with lowered springs, especially on the 5 who have the insufficient shocks on them from the factory to begin with.

 

[petitevan]

do KYB shocks work well with lowering springs? i wasn't thinking about lowering when i replaced the rear shocks.

You don't need to trim your stops if you use the right shocks with lowered springs to begin with. (ie. Koni yellows)
Never use stock shocks with lowered springs, especially on the 5 who have the insufficient shocks on them from the factory to begin with.

 

[DKaz]

KYB works with a maximum 1.5" drop.

 

[petitevan]

i should be fine then, thanks.

 

[ProjectBlack]

I just dropped my P5 yesterday with the Eibach Pro Kit, 1.6" in the front and 1.4" in the rear (I think). While we had everything apart we took about 1" off of each bump stop. Seems to work just fine, but I don't think I'm compressing all the way anyway. I also installed Tokico Blues.

 

[lomatic]

The Tein S-Tech's I just put on my 5 gave instructions for how much to cut off the bump stops. I cut right at an inch off of mine. Though the KYB bump stops were a bit shorter than stock so I'm not sure how much that would work out to.