I've had a few modern frames lately and, although I love 425mm chainstays, a bit more travel and slacker head angles, it all goes in the toilet when I have ridiculous pedal strikes. One hardtail frame I really wanted to love in particular, even with 170mm cranks was catching roots and small rocks all the time!
Low bb height and pedal strikes.
Mr. Blue Sky
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Yup, pretty much a myth perpetuated by people who aren't engineers and by bike manufacturers who want to sell an idea.
Simple math is all that's necessary:
5mm is what percentage of 1200mm?
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100% irrelevant
Not correct. BB height has to do with the BBD, or BB drop, which is the distance between the height of the BB and the center of the wheels. Have this negative and you'll have a hard time to even balance on a bike. The bigger BBD, more stable the bike will be.
I can say that my bike has a BB some 5mm lower than my previous one, depending on frame settings. At first I have several pedal strikes. After I got used to it, I'm faster with less (or the same) number of strikes. Remember, we're talking of a 5mm difference on a BBD from 25 to 30mm.
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So is most of this discussion and your point is?
I mean really, we got a guy comparing a 10mm change in BB height to a half degree change in HTA.
Then we got a guy who actually thinks he rails a corner way better because his BB is 1/4" lower.
Seriously, this is some pretty ludicrous stuff, at what point has this low BB benefit nonsense jumped the shark?
I would agree that raising the BB too much, like lowering the BB too much, could lead to problems, but we're talking about 5-10mm, not enough to matter in regards to handling, but clearly (based on rider feedback) enough to increase pedal strikes.
What sucks is that I've had to reduce my crank length to 165mm to make my bikes rideable, and the BB is still too low.
My BB threshold is 340mm for all mountain, and 345 for rock crawling, anything less is a PITA.
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BB drops and heights are relatively short distances so yeah 5-10mm is a big change. Decreasing your reach or chainstay length by 10mm are less drastic changes. I can feel the difference in my hardtail and enduro bike with the hardtail being easy to tip side to side. BMX bikes with their high BB (positive BB drop I think) are ultra obvious. I can tell the order of my three bikes' BB drop even though I haven't actually calculated the BB ride heights.
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Just a quick question as it seems many if you may know. I have an Intense Primer that came with a 34 130 fork. I’m considering a 34SC 120. It will suit my XC style more. I do not tend to have a lot of strikes now. I also run the rear shock in the 115 mode all the time. Lastly I run the sag at 25 percent and like a firm pedal platform. Will the 10mm shorter fork drop the BB height much? Any guesses if it would be substantial? HTA affect? Thanks in advance!
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I'd say 3mm per 10mm change in fork length is about average. You could strap a large velcro strap to the crown and arch to limit travel to see how you like it.
You can do an extended crown race or crown race spacer to make up for this if you want to keep the geo while going lighter with the fork.
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That is absolutely not true. :madman:
Explain how nobody ever complains about balance on these bikes:
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I don't know what that is but as I mentioned before BMX bikes have a positive BB drop and it's very noticeable how twitchy that makes the bike side to side. That doesn't mean it's hard to balance per se, it suits its purpose well, but that purpose isn't rough high speed mtb trails.
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Better yet, explain why anyone would ride that. I can't imagine someone riding that and not complaining about it afterwards. LOL
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Between this and railing about people breaking pr's on their new bikes I'm going to have to ignore.
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More power to ya, just need to watch those ski tips as you jump the shark
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I have a bike with a 425mm chainstay and a 308mm BB height (which is just over 12") and a 175mm crank. Yes, pedal strike is an issue if I'm not mindful of my pedal position cornering on technical single tracks. This thing handles well and rock steady on the downhills. I don't have to think about it, it is natural part of riding.
My Ripmo has 341mm BB and 175mm cranks. It has the lowest BB that I have ever owned and I got a lot of pedal strikes the first few months of riding it. I got better about the strikes and still get some, but I am constantly aware and am always thinking when I get close to something that I might strike so I flinch waiting for it. It is a mental thing now and I hate having that feeling! I am thinking about getting shorter cranks to help overcome the mental part of it.
[SUP][/SUP]
It used to be a 13.4 inch BB height was plenty. But today's suspension travel on average bikes is ever increasing, and what was once a high BB is now low. An example is the Ripmo, a 6" travel bike. All of a sudden, a 13.4" BB height is low (assuming a rider is using sag and all of the travel). And if you don't want to strike pedals on a 6" travel bike, you're probably getting into the mid 14" BB heights, which is high by almost everyone's standards. I guess that leaves some riders decreasing sag or getting 165mm cranks.
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