robertj298 

I have this 1989 Centurion Ironman I bought last year. It is one of my favorites. The problem I'm having is i
wanted to switch tires to a 28 or 25 mm tire from 23 mm. The original calipers were changed fro Suntour GPX
to Shimano 105s. I thought no big deal but it seems like neither 28s or 25s will fit without hitting the top of
the caliper on the rear brake. I think the front will fit but not the rear. I can't imagine Shimano 105s having this problem
Any recommendations? Here is a photo

Bianchigirll 

How is the clearance on the fridge itself? BTW you'll need a little room for deflection or whatever you want to call it when you put weight on the bike and the tire gets a bit bigger and you squash the bottom. Do you have a different caliper you can tryout?

Too bad they stole the GPX calipers, I'm not not a huge fan of DP brakes.

Classtime 

My son’s 89 expert has 6500 calipers and there is room for 25s but probably not 28s because of the bridge but I never tried.

icemilkcoffee 

There is still a big gap between the brake shoes and the rim. Adjust the brake to take away that slack, and see if it clears.

I had a '87 Ironman and there was plenty of room even with 28mm tires. I am very surprised that the '89 model is this tight.

robertj298 

It helped but at one spot it barely touches but the again thats without a full tire or the weight of a rider on it, I have 2 87 Ironmen
and they both have plenty of clearance

Classtime 

Was that ‘87 a Master? I think that year’s Master was like the ‘86 Classic which has plenty of room. My ‘87 Expert — not so much.

rccardr 

Put down the release levers. That series of brake shows lower when the release lever is up.
You should be able to fit 25mm tires.

icemilkcoffee 

How far forward is your rear axle in the dropout? Move it all the way back in the drop outs to see if it clears.

canklecat

Yeah, my '89 Ironman Expert with Suntour GPX group barely clears Conti GP Classic 700x25 tires. There's a raised center tread that makes the tire taller than usual, probably close to 700x28. Usually I just ride until the tire wears enough to stop scraping the brake bridge.

I'm planning to try some Conti Ultra Sport 3 in 700x28 on at least one road bike. If it scrapes the rear brake bridge I'll probably use a moto tool to file down the bridge just enough to clear some room.

AeroGut

If it’s just the caliper and not the bridge that’s in the way, an inelegant solution would be an upside down drop bolt to raise the caliper. Apparently they used to sell some that were made for shimano dual pivot brakes but they’re probably hard to find: https://www.sheldonbrown.com/dpdropbolt.html

georges1

Interesting maybe the geometry including the brake bridge changed slightly over the years but this is just my guess

nlerner

Two words: 650b conversion

robertj298 

It's strange I have an 87 Expert and 87 Master that have 25s on them and have room where I could put 28s on them.
I also had an 89 Expert just like this one that had a 4 cm larger frame and it had 28s on it. Maybe I'll just put the old
23s back on it

Mr. 66

Not something I would do on the normal, I've ground down a spacer to a wedge shaped. This can gain (or lower) a mm or two when tightening the caliper to the brake bridge.

robertj298 

Strange I have the same tire the same size on a different bike that measures 2 mm thinner

Kontact 

Have you tried the tires with a closed QR and adjusted caliper yet?

robertj298 

Yes it’s better but still rubs

robertj298 

I picked this bike up for a good price but wasn’t thrilled that some of the stock Suntour gpx parts were swapped. The wheels and hubs were switched to Bontrager Racelite and the brake calipers to Shimano 105s and the freewheel swapped to Shimano but the bike rides really nice but I’d like a little bigger tires

sd5782 

You may not want to get on a higher quality frame that can take 32s. You might actually add this one to your for sale listing. I just set up a Trek 412 with wonderful feeling 35s, but most of my fleet is 32s. Perhaps a full Reynolds 531 that can take at least a 32 is in your future. You seem to have a knack for finding them.

Kontact 

I recently built some wheels with similar profile rims. I find that the shorter, less aero rims ride like a bigger tire in their ability to absorb bumps.

shoota 

You hate stopping?

Bianchigirll 

Stopping is overrated.



I don't mind stopping one bit but considering we had centerpull brakes for decades before we had side pull and people weren't constantly dying because the brakes did not provide enough stopping power. Look at how cheap the brakes were on a Murray or Huffy "10 Speed" in the '70s and '80s and they were never labeled as death machines by the CPSC.

Dual Pivot brakes are like 'brifters', they provide an unnecessary improvement in performance.

georges1

And what about when you have stop very quickly in a emergency, single pivot weren't enough efficient apparently because 33 years Shimano introduce them with in1990 Dura Ace BR 7403, 2 years later Campy introduced the Record dual pivot brakes. Unnecessary improvement ? Debatable especially in an emergency stop or under rain. Maybe a comparison between stopping distances between a single pivot brakes and dual pivot brakes,will show the dramatic improvement in stopping.I think when you ride a road bike fast the goal is to stop when needed and not get into accident. The brifter thing is another debate,after Shimano ceased the production of the ST 7801 brifers,I stopped myself interesting to the new Dura Ace groupsets.

Kontact 

I don't know if the double pivot brakes actually grab the rim any better, but they do it with less force on the lever.

robertj298 There are lots of GPX calipers on ebay.

georges1

They do and if they are set properly well from the start, they are fantastic brakes