XT or XTR Hollowtech

Bike-Rich

Hi all,

I need to replace the Bottom Bracket on my Tourer (26"), external type.

I can get the XT for around £20 and the XTR for only a couple more. But, from what i've been reading sometimes the only added advantage from one level to the next is weight saving. Is this the case with the XTR?

As this is for a tour bike with heavy load durability is the main priority.

Thanks,

jimothy78

general consensus is that the XTR version is much better sealled, and lasts a lot longer. I've been running one offroad in absolutely filthy conditions for nearly a year now and it's still really smooth. probably worth the extra few pounds.

Bike-Rich

Thank you

The extra couple of £'s more is not a problem at all, just did not want to go for something that could be lighter at the cost of durability.

I can't really justify the cost of a Hope but there is still some life left in my current one, I plan to take the current one off and replace but still carry it as a replacement on tour. Should get me out of trouble if needed.

So to confirm, the XTR would make a good touring BB?

Thanks,

jimothy78

Bike-Rich wrote:

The extra couple of £'s more is not a problem at all, just did not want to go for something that could be lighter at the cost of durability.

Looking at the few user-measured weights available, it seems there is no difference - weights for both units seems to fall in the range 89-92g, so doesn't look like there should be any reason to suspect that XTR has been under-engineered to save weight any more than XT/SLX has.

So to confirm, the XTR would make a good touring BB?

As good, if not better than, any other HTII option. However, if you want to go for the ultimate in durability, then you may want to consider "rolling back" to good-old UN55 square taper

Bike-Rich

jimothy78 wrote:

As good, if not better than, any other HTII option. However, if you want to go for the ultimate in durability, then you may want to consider "rolling back" to good-old UN55 square taper

Thank you,

Ideally the square taper bottom bracket would be ideal, i'm still reading up on this but in the future I would like to up/downgrade to it.

Can this be done on a hollowtech 2 'hole' or is it different size?
The cranks would also need changing?

For now the XTR will be fine but it'll be good to know the above for future reference,

jimothy78

Yes, hollowtech II and square taper can both be used on the same bottom bracket shell as long as they have the same "thread" (the vast majority use "English thread").

After choosing a crankset, you need to get the BB with the right spindle length and shell width.

Spindle length is determined by the crankset itself, and is simply a case of looking it up on a table here.
Shell width is determined by your frame, and is usually 68mm or 73mm - if your existing HTII setup uses three spacers (two driveside and one non-driveside) then you'd need a 68mm square taper BB; if it uses just one (driveside) spacer, then you need a 73mm.

Yes, you'd also need a square-taper crankset, but you can often pick them up on ebay at very reasonable prices. In fact, you may well find you can get a decent used crankset plus a new ST bottom bracket for the same price as one of those XTR hollowtech II bottom brackets.

Bike-Rich

Many thanks, i've made a note of that info and will look into this for a next upgrade,

What was the reason Hollowtech became the standard when Internal is much more durable?

keef66

Bike-Rich wrote:

Many thanks, i've made a note of that info and will look into this for a next upgrade,

What was the reason Hollowtech became the standard when Internal is much more durable?

It's sold on the basis that it's a stiffer arrangement because the bearings are further apart and the axle is fatter.

In practice it seems that bearing alignment is sometimes less than perfect, and the bearing seals can be more prone to letting water in, possibly because they are sticking out from the BB shell in a constant stream of road filth when riding in the wet, so some experience problems prematurely.

IME I've had a 105 HT2 BB last 4 years of year round cycling (but with mudguards) before it started to develop an annoying creak. Replaced it with an Ultegra, only because CRC were selling them off for £11, and that's still silent after 2 years.

HT2 is a bit easier to work on than the old square taper stuff, and certainly more so than the Campag equivalents which sound a bit of a faff.

ugo.santalucia

When your rings wear out, consider a swap to squar taper...a UN 55 will be about 15 quid and you can get a customised double chainset from SPA cycles for 70-80 quid or so, on top of my head...

I have gone back to square taper from HT2 and Ultra Torque and I am a lot happier... there is no drawback, only advantages

Bike-Rich

I will do that Ugo, cheers

Thank you also keef for the explanation, made it much clearer.

jimothy78

Just something else I forgot to say earlier. You should get in the habit of differentiating between Hollowtech (one) and Hollowtech II, especially if you're going to look into square taper designs at some point (some of which may (correctly) be described as Hollowtech).

At first, Shimano used the term "Hollowtech" to describe crank arms that were hollow-forged to save weight. These Hollowtech cranks were either square taper or octalink designs and worked with internal bottom brackets of the same type.

Hollowtech II followed some time later, and is Shimano's name for the hollow-spindled, external bottom bracket system we're familiar with today. Unfortunately, a lot of people today just refer to this as "Hollowtech" but that can lead to confusion. Some Hollowtech II cranksets (Deore and below) use solid cranks arms, but the higher-end ones ( LX/SLX and above) use hollow crank arms, so are effectively using both Hollwtech (one) and Hollowtech II technologies, though you never see the former referred to in this situation.

mamba80

I have had on various mtb's, external and internal BBs using HT (octalink) and HT2 there is no discernible difference in durability, HT2 BB/Cranks are lot easier to work on, no weird crank pullers and odd shaped spacers and BB tools.
But I ve a set of octalinks cranks, triple - that I can sell you !

cycleclinic

I use a Token external BB. When the bearing wore out I replaced them with INA 6805 bearings (you can do this with the Token BB's as the plastic bearing cover can be removed easily without breaking it and the bearings are 7mm wide). Since I have done that the bearing have seen some nasty conditions and they keep on going.

ugo.santalucia

thecycleclinic wrote:

I use a Token external BB. When the bearing wore out I replaced them with INA 6805 bearings (you can do this with the Token BB's as the plastic bearing cover can be removed easily without breaking it and the bearings are 7mm wide). Since I have done that the bearing have seen some nasty conditions and they keep on going.

I wonder why Shimano doesn't offer a beefed up 7 mm wide option too... they do 17 different options of exactly the same thing... :roll:

jimothy78

ugo.santalucia wrote:

thecycleclinic wrote:

you can do this with the Token BB's as the plastic bearing cover can be removed easily without breaking it and the bearings are 7mm wide)

I wonder why Shimano doesn't offer a beefed up 7 mm wide option too... they do 17 different options of exactly the same thing... :roll:

That wouldn't really be "beefed up", just better sealed - the 6mm wide single-sealed shimano bearings are essentially 7mm double-sealed bearings with one side machined off to reduce them to 6mm - if you take the bearings out of a shimano HTII bb and check the code on the side it is actually gives you the code for a 37x25x7mm 2RS bearing.