Bump stops - technical data and application guides
Fat Cat Motorsports brought awareness of the art and science of bump stop tuning to the general enthusiast public. We've been talking about suspension travel and bump stops before it was fashionable. When you're looking to get better durability than typical factory bump stops or want a performance upgrade, FCM bump stop kits are a must-have with any suspension upgrade.
IMPORTANT! While we have created an application guide for street, sport, race suspension and have designed various FCM bump stop kits sold by 5XRacing.com, if you have questions you wish us to answer, you MUST fill out the FCM Elite consultation form and you MUST make a 30 min payment ($125, at the same link) before we can answer any specific questions on a custom bump stop or recommendations for spring rates, etc.
In more detail there are several reasons to consider FCM stops and bump stop kits. First, most factory stops are made from MDI - type MCU (micro-cellular polyurethane). It is lower cost and prone to faster wera during operation and thermal cycling than the higher quality and more expensive NDI and TODI. You can see here evidence from a partially disintegrated OE bump stop. Here's a short Youtube video showing worn OE rear stops.
Don't let this happen to you. We use the highest quality MCU (*micro*-cellular polyurethane) available. This safely maximizes suspension travel, increases comfort and enhances your driving enjoyment at the limit.
Second, the factory bump stops are typically designed to stiffen the front of the vehicle significantly during cornering. For an average driver this will be nearly unnoticeable but for an racer, enthusiast, or sport-oriented driver the increase in stiffness will be felt as 'understeer' or the vehicle turning under or less than the steering input. That added stiffness also tends to reduce available suspension travel and can cause a vehicle to be harsher during full compression events.
Third, changing bump stops by itself is not necessarily a 'cure-all', but it is an important part of evaluating whether the suspension is operation in the most efficient way for your needs.
Fourth, most aftermarket suspension suppliers of shock absorbers or lowering springs do not consider how important the bump stops are. As an example is the XIDA suspension by 949 Racing which uses short and quite stiff bump stops. Emilio and I had a conversation on Miata.net about this with some of their customers. I provided technical support that led to more stable, faster cars. Again, we realize not every individual will be able to afford an FCM Elite suspension or choose to give up the desire for knobs, but that doesn't mean they can't beneift from our technical / practical understanding and experience.
We have multiple resellers of FCM bump stop products, including our 36mm bump stop sold exclusively by 5X Racing which has 3 densities (soft, medium, and hard) available in the 36mm pattern.
If you have questions you wish us to answer, you MUST fill out the FCM Elite consultation form and you MUST make a 30 min payment ($125, at the same link) before we can answer any specific questions on a custom bump stop or recommendations for spring rates, etc.
IMPORTANT! While we have created an application guide for street, sport, race suspension and have designed various FCM bump stop kits sold by 5XRacing.com, if you have questions you wish us to answer, you MUST fill out the FCM Elite consultation form and you MUST make a 30 min payment ($125, at the same link) before we can answer any specific questions on a custom bump stop or recommendations for spring rates, etc.
Why use FCM stops instead of factory?
Our kits are provided as an integrated package (not just a part) and are designed for your particular setup. Anyone can sell a part (at double the cost), we provide a solution, making sure the suspension maintains a safe controlled behavior at full compression.In more detail there are several reasons to consider FCM stops and bump stop kits. First, most factory stops are made from MDI - type MCU (micro-cellular polyurethane). It is lower cost and prone to faster wera during operation and thermal cycling than the higher quality and more expensive NDI and TODI. You can see here evidence from a partially disintegrated OE bump stop. Here's a short Youtube video showing worn OE rear stops.
Don't let this happen to you. We use the highest quality MCU (*micro*-cellular polyurethane) available. This safely maximizes suspension travel, increases comfort and enhances your driving enjoyment at the limit.
Second, the factory bump stops are typically designed to stiffen the front of the vehicle significantly during cornering. For an average driver this will be nearly unnoticeable but for an racer, enthusiast, or sport-oriented driver the increase in stiffness will be felt as 'understeer' or the vehicle turning under or less than the steering input. That added stiffness also tends to reduce available suspension travel and can cause a vehicle to be harsher during full compression events.
Third, changing bump stops by itself is not necessarily a 'cure-all', but it is an important part of evaluating whether the suspension is operation in the most efficient way for your needs.
Fourth, most aftermarket suspension suppliers of shock absorbers or lowering springs do not consider how important the bump stops are. As an example is the XIDA suspension by 949 Racing which uses short and quite stiff bump stops. Emilio and I had a conversation on Miata.net about this with some of their customers. I provided technical support that led to more stable, faster cars. Again, we realize not every individual will be able to afford an FCM Elite suspension or choose to give up the desire for knobs, but that doesn't mean they can't beneift from our technical / practical understanding and experience.
We have multiple resellers of FCM bump stop products, including our 36mm bump stop sold exclusively by 5X Racing which has 3 densities (soft, medium, and hard) available in the 36mm pattern.
Review our bump stop application guide
Summary of benefits
- More compliance
- Greater durability and service life
- More consistent and predictable behavior in extreme situations
- Maximum suspension travel for best ride and handling
- Smooth bump stop engagement for excellent fine-tuning of suspension handling behaviors
- comfort and enhances your driving enjoyment at the limit
If you have questions you wish us to answer, you MUST fill out the FCM Elite consultation form and you MUST make a 30 min payment ($125, at the same link) before we can answer any specific questions on a custom bump stop or recommendations for spring rates, etc.
Got a question before scheduling an Elite Consult?
Please read about the uniqueness of being Elite, or explore our Elite Design Q&A. Then submit an Elite Inquiry form or ring the shop. We typically respond within 24 hours. To request a shop visit or demo ride, please contact us first.
408-221-8247