press fit BB's good, bad or just different?

Idly internet browsing for a new bike that I cant afford and noticed quite a few manufacturers are using them – guessing it makes BB swap a shop job unless you have fancy tools which seems like a PITA – are they noticeably stiffer like the sales patter suggests or just something different for the sake of it

I had the BB-90 on a Trek Elite, i think it has it’s merits however when it came to getting parts or having it serviced i found it a bit of a nightmare. I wouldn’t let it sway my choice of bike as such but i would choose non press-fit if I had the option.

Not a whole lot of advantages but I don’t see them any worse than an normal external BB. Although I bought the Shimano tools for mine you can do it with a headset press or DIY something.

Its a right royal pain in the behind, especially if you ever swap between say FSA and Shimano cranks that require different BB’s. I’ve found removal pretty much destroys the bb shell. Installation is easy with or without proper tools but that’s about it.

Not noticeably stiffer to the average person and definitely no longer lasting or better sealed cos it still uses the same style of crank and the same inherent issues.

It was one of the reasons I sold my Lapierre and a reason why I’d stay away from a press-fit bb frame in future unless the rest of the frame design was streets ahead and there was nothing else comparable.

as above pain in the arse to change and bearings lasted for alot less time than on a hollowtech external, this combined with changing the rest of the bearings on my lapierre is why I got rid.

I shall be finding out after this weekend when we go and pick up the SO’s new CX frame which has a BB30 shell, resulting in the enforced purchase of new shiny stuff……

Excellent service life, cheaper, stiffer more simple to fit/unfit Whats not to like.

Ran them on a road frame for 3 (2nd set only due to swapping C/set) seasons and now well into my 2nd year on the MTB.

I think they’re shit, I have one on my 2010 Trek Fuel EX 9, bearings were siezed and had to be replaced as well as new nylon bushes, these had to be altered to fit the cups, also I would like to run a chain device but can’t find one.

Now I will have to deisgn one and have it machined up, I would much prefer the older style thread fit, that said the bearings I have in it now should last about 18 months.

Its a bigger bearing that old style BBs and better supported than a HT11 type so should last better – however I really dislike the idea of being able to wear the frame fitting and removing them – I wonder how many new bearings can be fitted before they become loose

mtbtomo – Member
I’ve found removal pretty much destroys the bb shell.

really – so a £3k frame is foooked once the BB wears out ??

Must admit it has somewhat put me off a zesty. I notice cube use them too – seems a bit uneccesary?

and a reason why I’d stay away from a
press-fit bb frame in future

This.

It’s seems like it’s one less operation for the frmae builder not having to turn the thread into the frame.

I had one on my Scott Scale and by choice I’d not bother again as the bearings were pretty crap and as yet there are not many alternatives if any. I didn’t notice any extra stiffness from either my BB30 version or my BB86 version but I don’t think you would, you only notice when things are bad, not just a little better than good.

However a lot of bikes do now come with them and they do make the B/B area look tidier than a BSA fitment. It wouldn’t be a deal breaker for me but given the choice I’d stick with BSA.

Hello,

This post is only intended to help people with a little information. It is totally up to you if you believe it or not. Very few special tools needed.

About 4 months ago I bought a Boardman MTB Pro. I knew at the time some people have had problems with the BB30, even to the point of having bikes replaced by Halfords and the problem comes back !

At the 400 mile point, my BB became tighter (more than it was when new) and the bearings became notchy. I have a basic engineering and mechanical background, so with a little web searching and fiddling, I found the problem with my BB30. Basically the BB has been machined too tight for the bearing. A standard bearing fit for this sized bearing, as stated by bearing manufacturers, is about 12 microns, my Boardman is 50 microns! This is too tight for the bearings and is causing the stiff and notchy crank.

So here is my fix that will be carried out in the next few days when the bearings and tools come in.

PLEASE NOTE, I HAVE NOT DONE THE WORK ON MY BIKE YET AND IF YOU DO WHAT I AM INTENDING, YOU WILL LOSE YOUR WARRANTY. YOU DO THIS JOB AT YOUR OWN RISK !!

OK, now that’s out the way.

First fit a 10mm allen key into the non driven side of the FSA Comet crank and undo the bolt in the normal anti clockwise direction. Ignore the outer retaining nut that has holes in it. As somebody that has never seen this type of self extraction crank, this outer ring is just a retaining nut that gives the 10mm crank bolt something to push against for the self extracting crank action. As you undo the 10mm allen key, you will find that the crank is automatically pulled off its shaft splines.

Once the crank is removed, you need to drift the shaft out of the bearings. I found that a rubber ‘dead blow hammer’ was not enough. I placed a brass block onto the shaft and gave the shaft a few swift blows with a normal steel hammer. The bearing fitment onto the shaft was very tight on my bike, so required this extra force.

Once the shaft is removed with the driven crank attached, you will find that the bearings still feel notchy giving the impression of bad bearings.

The bearings at this point now need removing. I used a short length of 10mm steel bar with the end edges ground off so it was smooth and would not damage the bearing seats. You will need to give the bearings a few swift blows at about four points to move it away from the cir-clip. Once the bearing is off the cir-clip, you will be able to remove the cir-clip from it’s groove easily. It is very soft so I don’t think you would need the proper cir-clip pliers, maybe just two very small flat end screw drivers? I used an old pair of long nose pliers that I ground the tips to points. The cir-clips will not come out the BB at this point as the bearings stop them. This does not matter as all you are trying to do is get access to all sides of the bearings so they can be GENTLY drifted out with the smooth ended bar and hammer. Make SURE you hit the bearing on all side EVENLY until the bearings fall out.

You may well now find the bearings ‘seem’ perfect and not notchy at all. If you clean the outer race of the bearing and BB bearing seats and measure them with an ACCURATE digital vernier gauge, you should find the bearing seats are about 0.002″ smaller than the outer race of the bearings. That is your problem and no amount of bearing replacement, Halfords queueing or even whole bike replacements will fix this (assuming all the Boardman bike frames are machined the same).

What you now need to do is buy a small bore cylinder honing tool like the ‘Draper brake cylinder hone 25mm – 57mm honing tool 56244’. These can be bought for under £10 from ‘that’ auction site! You will also need to buy two new bearings, part number 6806-2RS. I am told that some bearing manufactures call them 6106-2RS (don’t know why) The size of the bearings are 42mm x 30mm x 7mm and have two rubber seals (2RS). I have bought SKF bearings at £18.50 each from my local bearing specialist, but much cheaper bearings can be bought from ‘that’ auction site for as little as £2 each! (but the cheaper ones will be of a lower quality).

With the bearings and cir-clips now removed, you must clean the bearing seats with a cloth and hone the seats with the honing tool. THIS WILL VOID YOUR WARRANTY! Fit the honing tool into a drill set to a slow speed. Lubricate one bearing seat with light oil, like WD-40. Compress the honing tool stones and put the tool into the BB making sure the stones are fully flat within the bore. Now simply start the drill and VERY GENTLY move the honing tool back and forth while turning to remove material from the bearing seat. Make sure you keep the stones lubricated and do not move the tool back and for too much. You must keep the stones nice and flat on the bearing seat. Periodically remove the tool, clean the oil off and measure the bearing seat.

You are looking for a -12 micron bore (0.0005″). That is to say the BB bearing seat needs to be 12 microns (1/2 a thou) SMALLER than the external diameter of the bearing you have. You will need a digital calliper to measure this.

Once you have honed the bearing seats to the correct size, you can clean the bearing seats and cir-clips with meths or other cleaner that will not leave an oil residue. Refit the cir-clips. Remove the rubber seals from the bearings and pack the bearings with a thick sticky grease and refit the seals. Clean the outside of the bearings with the cleaner you used for the seats and cir-clips.

You now need to refit the bearings. You will need to use a bearing retaining compound like ‘Locktite 641’. This is a medium strength retainer that will allow for disassembly. USING A RETAINING COMPOUND ON THE BEARINGS WILL VOID YOUR WARRANTY!

you will now find that the refitting of the bearings will not need any special tools. Just make SURE you tap the bearing home gently, making sure you use ALL sides of the bearing evenly. DO NOT HIT THE INNER RACE! or scratch the bearing seat. Wipe off the excess bearing retainer and allow the retainer to dry according to the brand you have.

Then simply push the driven crank shaft and its spacers back through the bearings until fully home. You may find that the crank shaft is a little tight. Do not force it in, simply polish it with 800 grit wet and dry paper (used wet) until the crank is a nice snug fit in the bearings. It may be a good idea to test fit the crank on the new bearings before fitting the bearings? It must not be loose and do not use retaining compound on the shaft. Then wind on the ‘pre-tension’ nut onto the back of the non driven crank, refit the alloy spacer making sure it is the right way around. Push the non driven crank onto its splines and do up the 10mm allen key bolt to a tension of 40 foot pounds. If you don’t have a torque wrench, 40 foot pounds would be quite hand tight with a long (6″ or 150mm) allen key.

Job done.

ALL THE ABOVE WORK WILL VOID YOUR WARRANTY AND IT IS ONLY MY OPINION, AT YOUR OWN RISK.

eh?

I have seen one, and heard of another frames made of plastic from a northern company, ‘stretching’ so any press fit bb just wobbles around 😯

They are replacing my mates frame (when they get stock!)…

I think this fad will pass rapidly.

Every one has forgot the most important reason why they are rubbish, You can’t have a bling colour to match the rest of your bike this is why external BB are the best, also you can use a chain device with external BB when their are no frame mounts for one.

Another piece of unnessary tech who was it that first brought out these Press BBs to go in the current mid/top range 2012 bikes was it shimano just like they brought out (in my opioin) 30 gears which i think are a waste of time. I am building a full susser this year and i am going back to double and bash (18 gears) with normal external BBs so i can easy replace them when they need doing.

Sorry, I didn’t mean BB shell. I meant BB cups.

I don’t see even with the correct removal tool, how you can get one out without damaging the soft, flimsy bb cups. They’re just not as substantial as headset cups, so easier to bend and mangle.

It maybe should last better because of bigger bearings which are better supported, but…..

External BB’s have always failed prematurely because of water and dirt ingress, not loading on the bearings. Its the bike industry solving a problem that didn’t exist. The truth is that its probably cheaper to produce frames for press-fit and similarly cheaper bb’s to suit.

I wish they would fix the sealing problem, which whilst better than it used to be still leaves a bit to be desired.

Sunbeam is saying………….

Don’t go for a frame with a press fit bb shell… Go for ordinary threaded 34.8mm (did I remember that right?) British standard BB shells

And I agree with him

Re Sunbeam’s post, I understand that the tolerances on a press fit bb may be incorrect but I don’t understand how they could get tighter and notchy after 400miles if its NOT because they’ve become worn. Something has changed in this 400 mile duration and it can only be worn bearings.

Making them a sloppier fit will just alleviate the symptoms of worn bearings surely?

I’ve had suspension pivot bearings out that feel notchy in the frame, but smooth when removed. New bearings will still feel smooth when fitted.