Legit Engineering Twist-Fit Bottom BracketLegit Engineering's new Twist-Fit bottom bracket has been designed to eliminate a lot of the headaches that come from a PressFit setup, including installation and removal troubles, as well as creaking that can often occur if the tolerances between the frame and cups aren't exactly bang-on. In fact, Legit guarantees their bottom brackets to run creek-free, which is saying quite a lot. They claim that they're able to do this by using a nylon ring that's wrapped around the cup interface, with the nylon making for a slightly oversized surface area compared to the diameter of standard cups. This setup is able to absorb the difference of out-of-tolerance bottom bracket shells, and it is also said to make for a completely noise-free interface between the cups and the shell. The nylon ring is replaceable, should you need to remove and reinstall the cups multiple times.
Legit has also made installing their bottom bracket a relatively easy job by designing the two sides to thread together. Yes, you'll still have to press one cup into the frame, but the opposite side pulls itself in as you thread it in. The bearings, which sit in the machined aluminum cups, can also be replaced without removing the cups from the bike. The Twist-Fit bottom bracket is available in pretty much any so-called standard that's out there, and versions equipped with regular sealed bearings retail for around $100 USD, depending on the model. Spending around $180 USD will get you a version with ceramic bearings.
Commencal Supreme DH V4The Supreme DH V4 made its debut at last weekend's World Cup race in Lourdes, France, but this is the first time that I've been able to get up close to the 220mm travel bike - it's a beauty in person, and probably one of the nicest looking high-pivot, idler-equipped machines that I've seen. The idler wheel is mounted in-line with the main pivot, and it's captured within the frame and surrounded by a plastic slider that keeps the noise down.
The bike's suspension design is very different to what the company has used on past bikes, although it is still classified as a single pivot system. Its extremely high main pivot works with a linkage that's located low on the frame, and there's also an idler pulley mounted inline with the pivot in order to prevent massive amounts of chain growth that would occur otherwise. Commencal is calling it the layout 'High Pivot Point', which is pretty self explanatory, and they said that it was first tested on a 160mm travel all-mountain bike to see if they liked how it performed and to fine tune pivot locations.
The shock is mounted nearly as low as possible on the frame, and it's compressed by a linkage that is said to provide a very similar feel to Commencal's previous downhill bike, at least in the first 200mm of travel, before supplying a ton of ramp-up in the last 20mm to keep the rider off the bottom of the stroke.
Chris Akrigg's Mongoose TeocaliWe all know that Chris is a bit of a wizard on a bike, but not even his own massive talent is enough to keep him out of trouble sometimes. Most of us remember the horrifying spill he had off the side of a small cliff, a fall that resulted in a compound fracture of his leg and some fancy titanium reinforcement, but he also re-broke that same leg a year after that accident while on a chill ride in an Austrian bike park. That second break, which was a spiral fracture, put him out for even more time, and Akrigg admits that it was more frustrating than the first because he was so amped to be returning from injury, only to be felled by an otherwise innocuous crash.
Chris is all mended up now, though, and he's back in the saddle and says that he feels like he's ready to get rowdy again, which means that we'll likely be treated to some mind-blowing action at some point in the future.
Chris says that he usually spends one day of the week on his moto trails bike, another on his trials bicycle, and the majority of his time on his medium-sized Mongoose Teocali that's pictured here. And while I expected the setup of his 160mm travel Teocali to be pretty out there - he does ride it like a trials bike, after all - Akrigg told me that his setup is actually not really strange at all. Both his FOX fork and shock are running standard air pressures for his weight, and the only thing worth noting is that he's using the largest volume spacer in his Float shock for maximum ramp-up.
He did say that he spends a ton of time riding clipped-in, which is surprising given what we see in his videos. A set of Hope platform pedals are pictured here, but the majority of Chris' riding consists of loops from his house, with stops at rowdy trials areas that he's built along the way. Cross-trials? Trials-country?
Be sure to check out all of our Sea Otter Classic images in this gallery.
Do people not prep their frames or something? Hell, it save shops time: they just need to check to make sure its pressed properly and not worry about either (A)Having to spend the time pulling out BBs and greasing threads or (B)Dealing with seized, ungreased BB shells.
But it makes me think 2 things.
1. What about the consumers? It's a pain in the ass when you get problems or scary sounds like creaking. On a carbon frame, that could mean something much more serious so it would make me pretty nervous. On top of that, who want's a creaky bike? Drives me nuts.
2. If it's about rigidity then why not change the standard of threaded BB to something of a wider diameter shell? I guess it's less about that and more about it being easier to make the frame. Finding ways to thread a carbon frame is kinda awkward but I think pressfits are too.
Maybe they'll find ways to make it better. For now, I'm avoiding getting a new carbon frame that's press fit.
As you thread the two BB cup halves together, the slots cut in one of the cup expands (collet), diameter increases and tightly grips the inside of your frame's BB shell.
This stops the cups "walking" or any movement / creaking caused by tolerance mismatch between frame BB shell and press fit BB. I've used this design on aluminium alloy and carbon fibre frames of both BB30 and PF30 variant with no issues.
BB30 most common problems were ongoing creaking and limited bearing life
These were caused by metal-on-metal contact from the bearing sitting directly on the aluminium alloy insert (for carbon) or metal shell (for a metallic frame) in the frame's bottom bracket, and poor tolerances on the diameter of the BB shell causing off-axis bearing loading, or vertical movement as crank axle tried to align left and right bearings.
The use of the wave washer and shim stack to preload the crank installation was also very crude and placed increased pressure on the bearing races.
Noise also came from metal-on-metal contact between crank axle and inside diameter of bearing. Shimano in contrast designed their HT2 cranks to be isolated from metal bearing by plastic bearing top hats.
Despite use of greases, anti-seize, copperslip, loctites, these noises would soon return causing a frustrating maintenance cycle of regular removal and refitting, for interference crank / axle designs from SRAM and FSA this repetition would soon damage the interface
PF30 alleviated the metal on metal contact by placing the bearings into a nylon cups before being pressed into the frame. However, poor tolerances on BB shell, nylon cups moving under heavy load and again crude preload mechanism with SRAM's 30mm crank pre-load collar (tighten until crank stops rocking!) placing increase pressure on bearing races.
as they say "User Friendly 73mm Threaded Bottom Bracket"
on my 2012 Stumpjumper 29'e Evo hardtail, I kept going through PF30 bearings, literally every few weeks. Constant clicking and creaking under power, it got really annoying, especially working as an experienced bike mechanic who does not like noisy bikes.
I assumed it was the SRAM 30mm single ring crankset, so sent it back to SRAM UK service centre, who said there was nothing wrong with it. Was it the pedals? Was is the chainring bolts? Was it the wheel skewers? Was it the headset? Was is the Fox 32 fork CSU. Dirt in the seatclamp? Round and round it went...
Several months later I'd had enough of replacing BB30 bearings and PF30 bearing cups.
Took the bike to Specialized UK, they measured the BB shell and found it was 0.2mm out of tolerance on the non-driveside cup. When you install the PF30 with bearing it would slightly compress the bearing, causing clicking and premature failure. They had not seen this before and spoke to their colleagues in the US.
Frame was toast, and made as part of a limited run. Several days later I was given a carbon fibre Stumpjumper frame as a free of charge upgrade as a warranty goodwill. Happy days!
Also I think I may have found my next downhill bike...
contemporary BMX are using press-fit BB with good success in the Mid and Spanish variations?
Only aluminium alloy and carbon race bikes are still using threaded ISO bottom brackets, typically to allow the use of a Shimano DXR HT2 crank or similar.
I was by the praxis booth on Friday and they said they couldn't make a functioning threaded BB insert for BB92. Very interested to see this and bummed I missed them at sea otter
I have an evolution by sitting in my garage right now.
www.albes.com/ProductImages/crankphotos/profileevolutionbottombkt.jpg.
my current press-fit BB is a wheels manufacturing PF30 which i only got because Praxis Works was not due in stock for 2 months when I rebuilt my frame.
After several short months of wet XC rides, the bearings are kaput in the wheels BB.
thankfully the Praxis is now back in stock so its time to swap out
Correct installation only works when fitments are within tolerance range, when the tolerance is too far outside the usable range, even correct installation will not prevent ongoing issues.
Loctite bearing fit compound, for example, has a limited gap-fill take-up capacity and will not prevent cups walking under rider weight and pedalling torque
As a workshop manager for leading stores in the UK, I've worked on 100's of press-fit BB for customers including all the modern systems running OE parts or retrofitted with aftermarket parts, and conversion systems designed to deal with common issues.
You may not be aware how common issues were with BB30 on Cannondale road bikes, or OSBB on Specialized road and mountain bikes. Manufacturers constantly came through with new "band aid" fixes to try and address these issues.
OSBB Carbon on Specialized road bike was getting so bad we were actually bonding the nylon cups with DP420 epoxy supplied by the manufacturer!
ep1.pinkbike.org/p6pb10994408/p5pb10994408.jpg
It was a real f*ck up though, and I noticed later frames (2015) started coming with aluminium alloy cups instead of the nylon cups we worked with!
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