Bumper Heights

Hey, everyone! My team has a bit of a problem, you see, R25 specifies that the bumper zone is 19cm (7 1/2 in) above the floor, and R31 says that bumper wood must be 127mm (5 1/2 in) tall. Our struggle is that, even having the bumper wood cut 127mm tall, we would over-pass the bumper zone. Has this happened to anyone else? How did you manage it?

You are going to have to mount your bumpers lower on your frame. If you can provide pictures, we may be able to help you figure out how to do that.


According to R31, the bumper wood has to be 5 inches, plus or minus 1/2 an inch.


To simplify the bumper zone think of it like this. The bumper is 5" tall. The top of the legal bumper zone is 7.5" from the floor. That means the max ground clearance you can have is 2.5" if you mount them as high as is legal.


Minimum BUMPER height is 4 1/2" per R31, BUMPER ZONE is 0 - 7 1/2" per R25 , therefore maximum clearance ground to bottom edge of BUMPER is 3".

I do agree that most teams tend to go with 5", as that is the way it historically (for some value of history) been done.

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The pool noodles are nominally 2-1/2" in diameter, and you have to stack two of them, making a nominal bumper height ~5".

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Serious question here. Pool noodles are specified as 2 1/2" (nominal) in R31C. Lots of noodles actually are smaller than this. In the past we have always gone with 5" plywood backing which sometimes results in a slight taper from the plywood to the noodles (when the noodles are centered). We have always passed inspection for BUMPERS.

Lots of noodles actually measure more like 2 1/4" or even 2 1/8" and tend not to make any specific size claims. If you find some slightly undersize noodles and deliberately cut your plywood to 4 1/2", gaining 1/2" of ground clearance (which can be huge in some designs) are you going to have issues at TECH?

From the 2018 Q&A. I’d expect the same answer this year if you asked.

Q29 Pool Noodle Size
Q: Rule book states “use a stacked pair of approximately 2½ in. (nominal) round, petal, or hex “pool noodles” (solid or hollow) as the BUMPER cushion material”, approximately and nominal are a little vague. How much variance is given in the size of pool noodles. 2 1/2 inch are hard to find, while noodles that are 2 - 2 1/4 are easy to find.
A: A “nominal” dimension is a dimension by which a product is marketed or sold but which may not match the actual dimension. No specific measurement variance is, or will be, specified.
(Asked by 4809 at Jan 11th 18)

R31. BUMPERS must be constructed as follows (see Figure 10-6):
A. be backed by ¾ in. (nominal) thick (~19mm) by 5 in. ± ½ in. (~127 mm ± 12.7 mm) tall
plywood or solid, robust wood. Small clearance pockets and/or access holes in the plywood
backing are permitted, as long as they do not significantly affect the structural integrity of

5 inches “plus or minus” 1/2 inch…so 4 1/2" would be ok but don’t make it an 1/16 of an inch smaller. Personally I would leave some wiggle room or be prepared with another wider set of bumpers.

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I have seen that Q&A. The issue is that some noodles don’t even make dimensional claims. We have always erred in the side of caution and gone with 5" plywood since that is what they tend to measure.

Assumeably, if you show up with 4 1/2" tall BUMPERS, and documentation that substantiates your claim of 2 1/2" pool noodles (even though they all measure 2 1/4"), you should be fine. Has anyone done this?

Do people seriously try to make their bumpers 4.5 in. or 5.5 in.? I’ve always assumed that the ± 1/2" was to account for the manufacturing slop that a lot of teams have, not so teams could strategically make smaller or larger bumpers. We always just try to make our bumpers 5 in.

If there’s a rule, teams will get as close to breaking it as they can manage if it offers an advantage.

Weight, height, frame perimeter, extension or whatever, teams will game the rule if they can.


We have not had a need to push the limits on BUMPER specs. However, we have designed and built right to the edge on the other size specs when needed. Last year our elevator was with 1/8" of the max. (Probably more like a 1/16" and yes we could prove it was rules compliant). However, if your design does not need it, it is ALWAYS a better idea to avoid designing to the max specs.

My concern is not with building down to the minimum of 4 1/2", it is how you prove your noodles are “nominal” 2 1/2".

Also, being rules compliant is being rules compliant. There is no “gaming the rule”, in being just under/over/or whatever the rule requires. Its binary (pass/fail), except when the GDC decides at the last minute to open up the Spec rules and turn failures into passes.