Eccentric BB?
Yesterday while working at the shop I had a bike in the stand with the above. So it got me thinking. If you were wanting to build up a bike with an IGH would you use an eccentric BB or sliding rear dropouts? And why?
Thanks! |
Originally Posted by Tandem Tom
(Post 21568375)
Yesterday while working at the shop I had a bike in the stand with the above. So it got me thinking. If you were wanting to build up a bike with an IGH would you use an eccentric BB or sliding rear dropouts? And why?
Thanks! |
Back when people were building more single speed bikes, this was a big decision people had to go through. I think a lot of builders did a couple of eccentrics and then got tired of the creaking complaints and switched to sliders. It's a pain to get an eccentric bb now, unless Nova has one and I've forgotten.
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Good timing as the frame I am waiting time to finish will have an IGH. No horizontal slotted drops, no BB eccentric. I will use a spring loaded chain tensioner. Or is that wrong:)? Why? because I have experienced sliders and hingers that slip and creak and still want a disk set up. Andy
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So to further my education a follow-up question. Doug you mentionef long horizontal dropouts. What about the sliding dropouts that are a seperate "piece"? My wife's touri g bike has these.
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Sliding or Rocker dropouts would be my preference over an eccentric BB. Sliders and rockers have their issues too, but the Paragon sliders are the best in terms of preventing slipping of the insert. Between the double bolt washer and the adjustment bolt at the front, they don't move after you set them. The cheap cast sliding dropouts are not so great in terms of preventing the insert from slipping in use.
Paragon rockers are good, if you get the Titanium 12pt bolts with them. The steel bolts that come with the dropouts do not hold up to the torque necessary to prevent the drive side from slipping forward under heavy pedaling loads, such as climbing while standing. The hex in the bolt will strip out before you can get them tight enough. |
good day dear all,
well good thoughts - i am glad to be here in this great forum. It is fantastic.
Originally Posted by dsaul
(Post 21569990)
Sliding or Rocker dropouts would be my preference over an eccentric BB. Sliders and rockers have their issues too, but the Paragon sliders are the best in terms of preventing slipping of the insert. Between the double bolt washer and the adjustment bolt at the front, they don't move after you set them. The cheap cast sliding dropouts are not so great in terms of preventing the insert from slipping in use.
Paragon rockers are good, if you get the Titanium 12pt bolts with them. The steel bolts that come with the dropouts do not hold up to the torque necessary to prevent the drive side from slipping forward under heavy pedaling loads, such as climbing while standing. The hex in the bolt will strip out before you can get them tight enough. |
Originally Posted by unterhausen
(Post 21568510)
Back when people were building more single speed bikes, this was a big decision people had to go through. I think a lot of builders did a couple of eccentrics and then got tired of the creaking complaints and switched to sliders. It's a pain to get an eccentric bb now, unless Nova has one and I've forgotten.
Were the creakers just the set-bolt types or all types? |
Originally Posted by Doug Fattic
(Post 21568473)
Tom it is much easier for an amateur builder to make a frame with horizontal long slot dropouts. This is because it is not necessary to nail exactly the chain stay length. You can get it approximately right by sliding the chain stays in and out of the BB shell’s sockets. With an eccentric shell it is necessary to get the miters and chain stay length just right. That is made much easier with machine mitering and an expensive fixture.
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Originally Posted by guy153
(Post 21713121)
But why is it necessary to get the chain-stay length exactly right? Obviously if it's way off you will alter the whole geometry but a mm or so won't make any difference.
Getting the chain stay lengths exactly right is one of the biggest challenges in building a frame. That is why it is wise for someone starting out to choose horizontal dropouts so any length discrepancy can be compensated for by dropout screw adjustors. The problem can also take care of itself if using an IGH or a single speed in long slot dropouts. I think every custom frame builder needs to hold at least a mm tolerance for wheels being centered. We should all take an oath that says we will hold to that standard. The problem is that a lazy/ignorant custom builder's work can tarnish the reputation of all builders. Even when they finally get to be acceptably good, their reputation (and by extension every builder's reputation) can be damaged by their 1st builds if they weren't up to standard. By the way Guy153, this post isn't directed to you personally but rather is a general statement to all builders and potential builders of the tolerances we should all accept. We are one of the few trades that has no standards of knowledge or ability to enter. Except what we can do to encourage and complement solid workmanship online and call out poor workmanship as unacceptable. https://cimg3.ibsrv.net/gimg/bikefor...dff959cf9.jpeg |
Originally Posted by Doug Fattic
(Post 21713460)
No 1 mm makes a noticeable difference. A bit off in chain or seat stay length is more important that other places. That is because of the ratio of length difference between the hub width and the distance to the rim/tire. That means 1 mm of stay length difference will move the tire/rim over almost 3mm. The tire won't just be 1mm closer to one side. [...]
Getting the chain stay lengths exactly right is one of the biggest challenges in building a frame. I do wonder if this is why bikes always used to have sort of diagonal horizontal dropouts. There's a bit of adjustment there for both CS and SS alignment just when fitting the wheel. If the OP uses an eccentric BB with vertical dropouts there's wiggle room in one axis and potential to file a bit in the other as a last resort. Similar with horizontal dropouts unless he goes with the diagonal ones. The least forgiving dropouts are of course thru-axles. |
I'm about to receive a bike with a PF30 shell and a Wheels Mfg. EBB adapter for a singlespeed setup. I will report back on how well it works. I see quit a few singlespeed bikes with PF30 these days.
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