Blog

Originally Published February 27, 2009

A few years ago when we first started doing the 650B conversions we didn't have a lot of information about which bikes might work on the wider 650B tires. There were many older bikes that were determined to work, but most of the newer bikes and frames were space constrained. So we went around measuring and test fitting wheels in various newer bikes and frames. Some of the shop guys thought we were wacky, and well, we probably are. But once you get that 650Bug it's energizing, and there are about a million 650B convertible bikes out there waiting to be transformed into something amazingly versatile and comfortable.

I had a Surly Pacer in my stable, a blue one that I got when Surly discontinued that color. I checked it and determined that it would be a good 650B conversion candidate; there was adequate room between the fork blades and the seat stays, and it had an impressive amount of space for tires between the "Fatties Fit Fine" chainstays. I told the 650B email list about this, and quite a few people made 650B conversions on the Pacer frameset. There probably haven't been many Pacer conversions lately, there are better choices available now if you're starting from scratch with a new frame. But there are a lot of Surly Pacers out there, The frame has been sold for years, and it's bombproof.

I own this bike, and I'd been thinking about converting it to 650B. Something I recently discovered moved me to do it, and I took it a bit further - I changed the front end. So this is a new twist on one of the first modern frames that we converted to 650B. 

The steel fork provided with the Pacer frameset is a sturdy affair, with a nice cast crown. But it is very heavy, and surprisingly, with respect to tire clearance, it's the narrowest part of the Pacer. Nonetheless, the original Pacer fork will fit a 650x38B with room for a fender, and the bike works just fine for 650B conversion. But I've always thought that it could be better. The steel fork on my 54cm frame has 45mm offset and a published 371mm axle to crown dimension. When I initially built my Pacer I guessed and cut the steerer tube a little too short, so I had to use different stem than what I had originally planned to get the bar where I wanted it. I've ridden the bike quite a few times on 700C wheels, taking it out as an alternative to other bikes that I own, and I always thought it did what Surly designed it to do. But I'm riding some other more interesting machines, and it didn't get much use last year.

Recently, when I needed to find a fork for a new cross frameset. I looked at some Bontrager Satellite Plus forks. There are several models of this fork, and they are still available as discontinued New Old Stock. They were produced for both caliper and cantilever brakes, and they have various crown diameters to match the outer diameter of your headtube. They were also produced with a couple of different fork rakes. These forks all commonly have a nice wide crown, with lots of room for tires and eyelets fenders. One more thing that appears to be common, however, is that they typically have a long axle to crown dimension. and they can raise the front of your bike, altering the angles and steering geometry a bit. For this reason, I chose a different fork for my cross rig.

But I started thinking about the caliper brake version of the Satellite, and there was that baby blue Pacer hanging on a hook at the back of my shop... I got an idea: What if I swapped out the steel fork and installed a new Bontrager Satellite Plus carbon fork! Hmm, I could even get the version with 50mm offset and make the front end geometry a little quicker, utilizing the added pneumatic trail induced by the bigger 650B tires. And - with that wide crown - I could run the biggest, fasted 650x42B Hetre tires, and still fit fenders. Finally, I'd have a chance to leave the steerer a bit longer and change the stem. Oh, I just had to try this, so I ordered the fork with the 50mm offset and a 45mm diameter crown. 

I got the bike ready for the retrofit. I disassembled the front end on the Pacer. I was concerned about damaging the alloy baseplate for the Ritchey WCS cartridge bearing headset, but it had to come off. I used a block of wood and a dead-blow hammer and I successfully tapped it off the steel fork without harm. Then I started thinking about the rest of the bike, and how I might want to change it for use as a 650B machine. I decided to change the Sachs 7 speed racing drivetrain and install a triple crank and 8 speed stuff. I had most of the parts, and I found a nice NOS Tiagra hollow-tech triple crank on closeout. This 9 speed crank would work great with my old XT rear derailleur, a SunTour XC9000 front changer, and some 8 speed shifters. I still needed fenders to round out the package. The SKS P-45 are easy to fit and they work well, so I went with them.

There was a Bontrager Select stem in the swap-out bin at Bikeman, and run inverted at -17 degrees, it would be level on the bike and fit my original 26.0mm Ritchey Biomax Pro handlebar. And of course I would run Tektro R556 dual pivot 73mm reach brakes in place of the short reach calipers. These are so much better than the centerpull calipers we used for those first conversions, especially with the Kool-Stop salmon pad inserts.

When the fork arrived I skipped downstairs to the shop and opened the box. Very nice! These are really handsome forks, with a nice finish and good details. I took some measurements... Hmm 383mm axle to crown by my measure, which is 12mm more than the stock fork. I had some concern about this, but there is something I had forgotten: Trigonometry. When you increase the fork offset you are effectively lengthening the base of a triangle, so it is necessary to lengthen the fork to compensate for this, otherwise the head tube will come down and the bike will actually be lower and the angles become steeper. So, the longer axle to crown dimension and the additional offset were complimentary, and as a result, other than the reduced trail which I desired, the geometry is unchanged. I now have the perfect fork for my purposes. A lightweight, stiff, and compliant carbon fork, with additional room for big 650B tires, eyelets for the fender, a longer steerer, and a lower trail ideally suited to the kind of 650B sport riding that I enjoy. This 650Bontrager Pacer now has same front end geometry as my Trek Pilot 2.1, and I think that's just fantastic! And yes, Fatties truly Fit Fine now - I can run 650x38B and even 650x42B Grand Bois Hetre tires front and rear with room to spare!

With Hetre 650x42B tires on the converted Pacer, the bottom bracket rides at 267mm - that's the old racing standard and it's nearly ideal for a bike like this. The brake swap was a snap, the Tektro R556 calipers are within their range of adjustment both front and rear, and I was able to reuse the cabling without issue. The SKS fenders fit easily, and the whole conversion came together very quickly and almost spontaneously after I decided on the fork swap. I'm running on borrowed wheels for now, but I'll lace up another set of Velocity Synergy rims and have a 650B wheelset just for this machine.

I put some Shimano PD-A520 pedals on it, I like those pedals on my 650B conversions - I'll have to do a review on them sometime. I may add interrupter levers to the brake system, but that can come later after I spend more time aboard the bike. I'm still not sure about the in-your-face Surly graphics, but I guess that's part of the identity of this model and brand, and for now it's there for all the world to see - it's surely one Surly 650B.

So, I finally got around to converting my own Pacer. A 650B converted Pacer is something old, but this carbon fork is something new, the wheels are borrowed, and yes, this bike is blue.;-)

Ed 650Braley