AntHill

Hi

I've not built a bike before and its now time to pick out a BB and Chainset. I have two queries i hope you can help advise:

1) What BB for a Surly Long Haul Trucker? I'm looking at a Shimano UN54 but i'm not sure what length i need? Some people use 113mm and some 110mm.

2) I have a mountain bike chainset at 44/32/22 and a road bike at 30/39/52. I much prefer to ride the road bike and find this very comfortable. My rear cassette on my LHT is Shimano XT M770 9 Speed Cassette a 11-34T so what are my options? I don't really like 44/32/22 setup, so I was thinking of perhaps the Shimano XT M771 Triple 9 Speed Chainset 48/36/26 as a happy medium. I guess i can't use a road chainset on this cassette, or does it make no difference?

Thank you for your help.

Ant

Garthr

From Surly .... you can use a maximum ring size of 42/53t double, 38/52/56t triple on the LHT. More or less ,any crank you want .

A Sugino XD2 with 24/36/46 or 48 and an 11t sprocket is more than a high enough gear, and should be low enough, depending on your strength, terrain and weight carried.
An XT would work fine too. I prefer the 110/74 BCD myself because rings are inexpensive, easy to find. Simano has a way of making their rings specialized per crank. I don't know if the XT is like that or not.

Cyclesafe

+1

If your only concern is riding loaded (35-50 lbs) then even this gearing is most likely too high. If you have flat bars (w/bar ends for had positions!) you can go with a typical MTB 22/32/44 drivetrain or a new 2x10 39-26 affair to avoid the triming required with a triple FD. For drops, you'll need to go friction shifting unless you frankenbike.

AntHill

cheers guys! i'll be using drop bars with bar end shifters.

what about bottom bracket?

robow

The bottom bracket design and length will depend entirely on which crankset you select. You will often find them sold together, as long as it is English threaded (which almost all are).

Garthr

If you use a Sugino XD2, use a 110mm UN 54 BB. This is what even Surly recommended when they spec'd it on their complete LHT's, for a 45mm chainline.

EKW in DC

Check out the recommendations here: https://www.sheldonbrown.com/bbsize.html

Doug64

This is a set up that might be worth considering:
Sugino DX 500 44/32/22
IRD 103mm Bottom bracket (68mm shell, 45-47mm chainline)
Tiagra 4503 Triple front derailleur
Shimano 11-34 rear casette
Shimano LX RD
Tiagra STI shifters

This setup on my LHT. We have put the same combination on several other bikes and it works well.

Tourist in MSN

Bottom bracket length varies by brand and model of crankset. You have to decide on which crankset you need first.

I prefer road over mountain bike cranksets, but if you are in a hilly area you would want to remove the 30t and install a 24t chainring. You may want to double check what the road crank is, it might be a 52/42/30, not the 52/39/30 that you cite. If it is 52/42/XX, you would have gearing that is close to one and a half steps between the 52 and 42. (This means that a shift on the front would be one and a half times as much gear change as a shift on the rear.)

A few cautions - a 52 on the front and 34 on the rear would need a few more chain links than come with a normal chain. The bike shop would have to provide a few more links when you buy. Although you should not ride in that gear (52/34) because when you are that cross chained you wear out components faster, you should have enough chain so that the drive train won't bind up in that gear. If you have that much chain, you will have tooooo much chain when you are on the 24t front (assuming you take my advice and change the 30t front for a 24t) and 11 or 12 or 14 rear, as your rear deraileur cage won't take up the slack. But, you should not use the smallest front chainring and the couple smallest rear gears anyway, so this is not really an issue.

I have a 52/42/24 front and eight speed SRAM 11-32 rear and am quite happy with it. The upshift from the 24t to the 42t is not a smooth shift, but I only use the 24t when I need the low gears for steep uphills so I rarely have to make that upshift.

BigBlueToe

My view is that, for loaded touring, having a low gear range is crucial. Having a high gear is frosting on the cake but not necessary. I don't like to tour with less than a 24 tooth granny, and would find a 22 no problem. However, having a 30 tooth granny would be unnacceptable. I have one on my road bike and it's nice when I'm not carrying a load, but I've been on several tours that included all-day climbs up steep roads - like when you have to go over a pass. My knees would have blown up with a 30-tooth granny.

I know the rear gears matter too. I have a wide-range 9-speed on my tourer and a narrower-range 10-speed on my road bike. My comments about the grannies still apply.

robow

tourist msn,
just curious if you've ever thrown a chain on the way down or had real difficulty on the way up since that 28 tooth spread is well above what Shimano recomends for their derailleur?

Tourist in MSN

To robow who asked a question in the above post:

I have not had the chain go where it should not go on shifting between the 24t and 42t. I installed a chain keeper on both bikes this year, but I rode several years without that without any problem. I installed it this year because I found a couple of them on sale and I figured it was worth the $4 that I paid. The ramps and pins on the 42t ring are not designed for the 24t, so shifting up to the 42t is not very smooth, but I can usually make that shift in a distance of 30 to 50 feet of travel. You clearly need a friction front shifter, not indexed for this setup.



The dirt shown is after completed tour last year. Photo does not show rear deraileur, it is an older XT, I think an M739 or maybe M737. Photo does show the vintage Suntour front deraileur.

robow

Thanks tourist MSN for the clarification as I wondered if you weren't using friction shiftng and chain keepers (smart). I just didn't want people to think they could do this with their index STI.

TimeTravel_0

would a low of 28-30 gear inches be acceptable for light-touring or touring with a moderate load?

LeeG

depends

Garthr

As Lee said, depends on the rider and terrain. When I was younger, stronger , I toured with a 14-28 or 30, and a 40/50 tooth crank. This was with moderate heavy load and some killer Mississippi River valley hills . It went just fine. Those days you just rode, didn't really think about all this stuff we do today.

So, who's to say. Know your strengths.

cyccommute 

The FC-M771 is a good choice but it can be hard to find in the US. The Shimano Deore M590 crank can be found for as little as $82. The M590 will take a 22 tooth inner if you want a low gear like your mountain bike crank but a high near that or the road bike. At $82, the Deore crank is a excellent deal and much better, in my opinion, than the Sugino. Just the ease of installation is worth the extra dollars...oh...wait...it costs less

Edit: Oops. Just noticed you are in the UK. Getting an XT 771 in Europe is much easier. If cost is an issue, however, look at the Deore.

P.Pilot

I'm looking to swap out my existing Ritchey crankset as well and was under the impression that the choice is limited by the frame BB shell size.

I really want to put a set of robust VO triples with a 74mm shell size but I thought the limitation is that you can't install anything that won't fit into the Surly range of 68mm.

Am I reading into this the wrong way or is the BB able to be modified? I really don't want to plunk down nearly $300 for a stock set of Whirly Cranks. Any other triple crank suggestions that will work on the Surly?

oldride

P.Pilot If you have a Surly LHT the BB shell width is 68mm. You will need to use a 68mm BB but the BB spindle (axle) comes in several lengths. You need to match the spindle length to the crankset.

EKW in DC

oldride is right about the shell width.

As for spindle length, the fountain of knoweldge that is the site of the venerable Sheldon Brown provides some great information.

https://www.sheldonbrown.com/bbsize.html

edtrek

I'm using a 20-32-46 chainring, and a 34-11 cassette on my LHT. My granny gear is 16".

I've never suffered from not having a larger high gear. I like the very low end a lot.

P.Pilot

I understand that, but my question is if it is possible to swap out the existing BB with a one than can accomodate a crank that requires say a 74mm shell.

cyccommute 

Spacers are your friend Most of the external bearing cranks use spacers to so that they fit 68 or 74mm bottom brackets.

P.Pilot

Ordered a set of Sugino Cranks and I suppose I'll have to settle with a Shimano sealed 68x110 BB's. Time to choose the right derailleur's and start looking for a cassette that doesn't let the chain jump around on the small (low gears?). I need to find out how to determine the chain length parameters. Can anyone lead the way?

Surly213

I am curious your feelings. I am building an older Long Haul Trucker 26" frame. I am deciding BB and cranks, chainrings and cassette. What is the Widest range "Recommended" without being overkill.
I Would like to run a Big roadie ring and a small in the front, 3 rings. And cassette??