Bikeguide.org - Bike maintenance for BMX'ers
The Street => The Bike Shop => Topic started by: blueee on November 18, 2017, 12:04:15 PM
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so I finally caved in and got a frame with a mid bb, one mid bearing weighs as much as like 2spanish bearings. all this extra weight is very upsetting
could it be possible to fabricate a lil aluminum spacer thingy to put between a mid bb she'll and a Spanish bearing? just a thought
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Mid bearing outer diameter: 41.275mm
Spanish outer diam: 37mm
A lot closer in weight than you suggest. Add in a 2.1375mm cup (with lip to locate the bearing) and the weight loss (for the MIDDLE of your bike where rotational weight is 1:1 not 2:1 or 1.5:1) and you're really not acheiving anything but overly complicating things for yourself, paying money and/or spending time on a machine
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I wouldn't it simply be like an oddshaped washer with a lip on it? what if I were to use a Euro bb bearing so the thingy had more substance and less steel in the bearing? o?
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Bluee are you thinking along the lines of a non concentric BB adaptor or just to fit the smaller bearings? If its just to fit the bearings Professor Horatio Hufnagel has it cold. Think of the heavy ass old American BB adapters, not worth it.
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You can save weight by not running the tube spacer. Seriously
Haven’t been running one for years and the mid bearings are beefy enough to handle it
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I should definitely drill holes in my tube spacer
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Apart from being terrible for your BB bearings (which are radial, not thrust or ACB, i.e. engineered for axial loads), not running a tube spacer will lead to your sprocket bolt coming undone, and your spindle bolts too if you don't have pinchbolt cranks. One of the subtle things that 99/100 people don't realise, like how most hub wobble in hubs with a 14mm or 3/8" axle is caused by non-parallel dropouts or exploded driver bearings being caused by the bearing shoulder on the axle not being a right angle but instead a curve
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i did that once some time ago. you need to make a custom tube spacer too probably. All in all saved 40 grams over Mid ircc and was a cool exercise on tolerances.
you could even buy them from khe back in the days
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wow, over an oz in savings, almost two! any chance I can buy the cups off you?
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1.4 by my count
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Just cut your crankarms off.
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That joke falls flat, I presume you had to do it over a hip to get it there
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Could always try and get some sealant or glue and try and center your bearing in the frame. If you use silicone it might also work as a suspension for your cranks, haha.
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He'd probably take that seriously in the quest to make his 11,340g bike weigh 11,300g
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Something you might be interested in. Spanish to Mid cup.
https://www.facebook.com/TeamScrapbikes/photos/a.544951209030694.1073741835.268999476625870/721409728051507/?type=3&theater
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I wonder why they don't make carbon fiber bottom bracket spacers?
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Because kids who ride BMX are poor.
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Carlos, why stop at Spanish? They're SO heavy! Euro too! Why not just run bushings??!!
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With laz's good sense in materials and Carlos's engineering that eastern bushing bb can live again.
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I'm sure Bitzer would invest
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Carlos, why stop at Spanish? They're SO heavy! Euro too! Why not just run bushings??!!
I actually tried the KHE gen. 1 bushings as I had a problem with my cranks spinning whenever I took my feet off (rode some flatland at the time). It was sooooooo annoying to ride with. Would have to kick-start each crank.
They added a small bearing in the gen 2. It is still a silly idea but for someone like you it might be interesting.
https://www.khebikes.com/bmx-teile/antrieb-mehr/tretlager/720-khe-bush-tretlagerset-mid-bb-p2-82
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You could also take a look at 34R ORTO bushing BB's, they come in Span and Mid, 19-22mm, I've used both Span and Midd in 22mm and they are awesome+light. Won't work well with Wedge cranks aka Odyssey Wom/Twom and Thunder. You use the crank arms bolt as tension on the BB for how much resistance/drag you wan't. Very Nice.
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With laz's good sense in materials and Carlos's engineering that eastern bushing bb can live again.
I can get an old Bizhouse one from the local shop for next to nothing haha, I was always skeptical about those though.
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Those bushings that you odn't use a tube spacer with have some serious issues. If you have pinch bolt cranks, your sprocket will move on the spindle and the bolt will come undone. If you don't have pinch bolt cranks, your crank arms will move on the spindle and the spindle bolts will come undone too. Not to mention that without a tube spacer, dropping the bike on the cranks/pedals is no good for the bushing/bearing on that side of the BB...
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Those bushings that you odn't use a tube spacer with have some serious issues. If you have pinch bolt cranks, your sprocket will move on the spindle and the bolt will come undone. If you don't have pinch bolt cranks, your crank arms will move on the spindle and the spindle bolts will come undone too. Not to mention that without a tube spacer, dropping the bike on the cranks/pedals is no good for the bushing/bearing on that side of the BB...
Yeah, I rode it with a profile set and tried my best to make it work. If I tightened the cranks enough for it to not come loose I couldnt crank and if I did it enough for my cranks to spin the cranks would come loose really quickly. Had to use a lot of lochtigh but was still too annoying in the end so changed back to regular bearings.
Used a splined drive sprocket so had no issue with the sprocket.
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some entry level bikes used Mid size BB (simple tube w/o any bearing stopper), steel or alloy cup with Spanish BB.
Make no sense, cheap for OEM, but extra parts, fitting, creaking, tolerances issue, etc