Author Topic: carbon short-drop rim-brake frames taking 28mm tyres  (Read 669 times)

carbon short-drop rim-brake frames taking 28mm tyres
« on: September 21, 2019, 03:51:46 pm »
I’ve reached the point where I can no longer tolerate riding tyres narrower than 28mm on Britain’s decaying, appallingly maintained and ubiquitously coarse-chipsealed road network. 

All my bikes except one are now fitted with tyres at least 28mm wide, so to get the final bike back into use I am looking for a new carbon fibre road frame that takes short-drop rim brakes but can accommodate 28mm tyres.  Ideally this capability will be evidenced by real-world confirmation of such 28mm clearance.

As I’ll be transferring components from an existing 25mm-max bike (which irritatingly has brake shoes at the top of their slots and very narrow seatstay/chainstay gaps), the new frame needs to meet the following criteria.  Any suggestions?

Essential criteria:
•   Available as frameset only
•   Standard-mount rim brakes (i.e. not direct-mount)
•   Standard short-drop brakes but able to accommodate 28mm tyres (mudguard clearance not required)
•   Standard 100mmF/130mmR q/r dropouts
•   Only interested in new unused frames

Desirable criteria:
•   BSA-threaded bottom bracket (preferred, but will reluctantly consider press-fit if can take Token/Hambini or similar type adapters)
•   Replacement gear hangers also available to buy
•   Below £1,000

Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #1 on: September 21, 2019, 06:10:18 pm »
have you considered the planet X EC-130 frameset?   IIRC short reach brakes are set with the brake blocks near the bottom of the slots on this frameset which bodes well for fitting wider tyres.  One of my chums has one of these bikes and IIRC GP-5000 tyres in 25mm come up large on the rims, so are about 26mm or so in size.  I don't remember them running especially close to the frame/fork, so maybe 28mm tyres are possible? I can probably check again if you like.

Of course the other aspect of ride quality is fork flex.  As with many modern bikes there seems to be little of this, so I don't think it is a comfy ride per se, even if it will take wide tyres....

cheers

BrianI

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Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #2 on: September 21, 2019, 06:25:16 pm »
Why not consider longer drop brakes if that gives you more options for larger sized tyres?

Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #3 on: September 21, 2019, 07:22:14 pm »
have you considered the planet X EC-130 frameset?   IIRC short reach brakes are set with the brake blocks near the bottom of the slots on this frameset which bodes well for fitting wider tyres.  One of my chums has one of these bikes and IIRC GP-5000 tyres in 25mm come up large on the rims, so are about 26mm or so in size.  I don't remember them running especially close to the frame/fork, so maybe 28mm tyres are possible? I can probably check again if you like.

Thanks for the suggestion, Brucey.  Have taken a look at the webpage for the EC-130E, which is presumably the same as the EC-130, and it is potentially a candidate - nice to see the BSA bottom bracket.

Unfortunately, though, PlanetX states a maximum of 25mm.  Of course, they might be being somewhat conservative, or might not actually have checked the real clearance....or they might be right.  However, the bike will get used for a lot of hard out-of-the-saddle riding up steep hills, meaning enough side clearance for wheel flex will be important......so if you do get the opportunity to assess the actual clearance that would be most helpful...….strategically angled close-up photos would be a bonus too.  Thanks in advance!!  The brakes I'm using are Ultegra 6800 front and rear.

Ideally, my target frame will accommodate '28mm' GP4000S II tyres, which measure about 28.5-29.0mm on 15mm ID rims.  If not, the '28mm' GP5000 tyres which are a bit narrower would do and are much nicer to ride than 25mm tyres.  '28mm' GP5000 is definitely as narrow as I want to go!

Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #4 on: September 21, 2019, 07:28:53 pm »
Why not consider longer drop brakes if that gives you more options for larger sized tyres?

Well, I have considered this, but I already have the brakes (Ultegra 6800, which are superb in the dry), along with all the other components, and want to keep this to a frameset-only conversion as far as possible with no additional outlay. 

If I can't do it via Plan A, then deep-drop is likely to be Plan B......although light deep-drop carbon fibre rim-brake frames seem to be getting thin on the ground now.

vorsprung

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Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #5 on: September 22, 2019, 12:55:16 pm »
My Specialized Roubaix does 28mm.  It just will take 30mm but it's a squeeze.  I usually have it with either 28mm and no guards or 25mm with guards

But you can't get this frame new now, this is a 2010 one.  Specialized Roubaix now have disks

Most bikes that take a slightly larger tyre have disks.  For example the Cannondale Synapse and Giant Defy are now with disks

I guess you might find a "new old stock" frame but really the easiest thing is to switch to disks
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vorsprung

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Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #6 on: September 22, 2019, 01:10:44 pm »
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Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #7 on: September 22, 2019, 02:17:47 pm »
I just had a go on my ubiquitous cheapo Planet X Pro Carbon, which they still sell new. Test was with a 19mm internal width front wheel* and a 28mm Gatorskin. It has 5800 brakes and the pads sit half way down the slots.

The front has maybe 3mm of clearance vertically from the fork crown, widening a lot either side. The back 3-5mm all round, especially at the BB, so I'd expect rubbage.

(* also used to mock up the rear test - the 28s are on my disc bike and I CBAed actually swapping the tyres)

Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #8 on: September 22, 2019, 08:26:19 pm »






tyres are 25mm GP5000 and (on those rims) measure exactly 27mm wide and are about 26mm tall off the rim.  There is bags of room at the chainstays.  Gaps elsewhere are about 4-5mm.  So 30mm tyres would be pushing it but (real) 28mm tyres ought to fit OK?

Frameset is a P-X EC-130-E bought about nine months ago.

cheers

Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #9 on: September 22, 2019, 09:20:19 pm »
the easiest thing is to switch to disks

That basically means a new bike.  I already have road disc brakes in my armoury, but there is still a place for rim brakes in my riding, and this exercise is intended to address that in view of my termination of sub-28mm tyres as an option on UK roads.

Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #10 on: September 22, 2019, 09:23:01 pm »
I just had a go on my ubiquitous cheapo Planet X Pro Carbon, which they still sell new. Test was with a 19mm internal width front wheel* and a 28mm Gatorskin. It has 5800 brakes and the pads sit half way down the slots.

The front has maybe 3mm of clearance vertically from the fork crown, widening a lot either side. The back 3-5mm all round, especially at the BB, so I'd expect rubbage.

(* also used to mock up the rear test - the 28s are on my disc bike and I CBAed actually swapping the tyres)

Thanks for doing that test.

How does the Gatorskin measure up on the 19mm rim?

I haven't bought a '28mm' Gatorskin for a few years, but all the ones I've ever had came up narrow, barely scraping over 26mm wide and 24mm tall on 15mm rims.  I always viewed them as slightly oversize 25s, from a practical perspective, but maybe Continental has corrected its Gatorskin dimensions like it did with the '28mm' 4Season (which similarly used to measure narrow but now thankfully comes as a proper 28mm tyre).

Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #11 on: September 22, 2019, 09:31:01 pm »
Thanks for going to the trouble of taking photos, Brucey - very useful.

I'm curious about the rim internal width on that bike.  The dimensions you've given in relation to the 25mm GP5000 are exactly the same as the dimensions I measure using a digital Vernier on my '28mm' GP5000 non-TL tyre, on a 15mm rim at 55psi - 27mm wide and 26mm tall!

Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #12 on: September 22, 2019, 10:18:24 pm »
I think the rims are  a gnat's under 19mm internal width. The model is  Vision team 35 IIRC.  The width I measured is exactly 27.0mm  (using digital verniers) but the height measurement can't easily be taken with the same accuracy. I didn't dilly-dally; I was getting rained on as I was taking the photos, the spots you can see in the photos are raindrops...

I think that the actual  sizes of various GP5000 tyres are listed on the Bicycle rolling resistance site, when fitted to a 17mm rim or something.  On most other rims the 25s do come up a fair bit smaller. From the sounds of it if you are going to use 15mm rims then 28s will be about the same size as 25s on the 19mm  rims.

cheers

Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #13 on: September 24, 2019, 01:08:31 pm »
I am led to understand that frames with direct mount dual pivot brakes allow more clearance. Few about though, top end Bianchi and latest S-Works Tarmac rim brake version are two. I’d still want to check clearance though.

Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #14 on: September 25, 2019, 01:25:55 am »
I think the rims are  a gnat's under 19mm internal width. The model is  Vision team 35 IIRC.  The width I measured is exactly 27.0mm  (using digital verniers) but the height measurement can't easily be taken with the same accuracy. I didn't dilly-dally; I was getting rained on as I was taking the photos, the spots you can see in the photos are raindrops...

I think that the actual  sizes of various GP5000 tyres are listed on the Bicycle rolling resistance site, when fitted to a 17mm rim or something.  On most other rims the 25s do come up a fair bit smaller. From the sounds of it if you are going to use 15mm rims then 28s will be about the same size as 25s on the 19mm  rims.

Thanks.  Interesting how the difference in rim internal width, and the relative pressures (whatever they are - mine was 55psi), can make two ostensibly different tyre sizes in the same tyre model effectively the same size.

I've always found Bicycle Rolling Resistance a fairly useful resource, although I'm mindful of the fact he uses 100psi for much of the road tyre testing dimension data, whatever the tyre size, means that I need to make significant adjustments when utilising his data sometimes.

Re: carbon short-drop rim-brake frames taking 28mm tyres
« Reply #15 on: September 27, 2019, 08:48:58 pm »
Well I’ve found a solution that I’m fairly sure I’ll be happy with.

I went for a Dolan Dual frameset for the frame transplant. This is ostensibly a deep-drop frameset, but I will be able to use it with my short-drop Ultegra 6800 brakes with some judicious jiggery-pokery.

Firstly, the Dual’s fork is clearly a proper deep-drop fork, although the 6800 brake would probably work with some offset brake shoes such as BDOP or Aican. However, as luck would have it, I happen to have a spare fork of similar design that would substitute quite nicely. This spare fork came as part of an audax frameset I built up a few years ago, but whose fork I subsequently replaced and shelved as although it was declared to be deep-drop, it wasn’t sufficiently deep-drop to meet my requirement. Having test-fitted the 6800 brake on the spare fork, with the shoes at the bottom of their slots there are a couple of mm to spare to the top of the rim.

So I’m pleased to be able to bring a seemingly redundant hardly-used fork back into service, and it matches the Dual dimensions and colour scheme pretty well. The steerer is also the right length for the new Dual, conveniently.

Secondly, the Dual’s seatstay bridge is set at a height that would put the shoes near the top of a deep-drop brake. This means that I’ll be able to use the short-drop 6800 brake if I file the slots deeper by 2mm on the left arm and 1mm on the right arm, which would give a small amount of rim height contingency as the pads wear.

I’ve filed brake slots deeper before – on a BR-650 deep-drop rear brake that was 3-4mm too short. This worked well, and removing that much material hasn’t weakened the stirrups enough to cause any problems or concern me at all, and it’s only the rear after all. So filing 1-2mm off the slots on the Dual’s rear 6800 brake, which admittedly has a bit less excess metal below the slots than the BR-650, doesn’t concern me either, given that too is a rear.

The only thing bothering me is the amount of filing effort involved. I remember it being a lot of work with the BR-650, using a small round file, and quite awkward. Is there a better, maybe powered, tool to do this with, that would make shorter/easier work of it?

All in all it’s a good solution:
• Fast mudguardless bike back in use, but now with tyres more suitable for fast riding on Britain’s crumbling road surfaces
• Even has clearance now for 32mm GP5000 tyres should I feel so inclined
• Spare, seemingly redundant, carbon fork brought back into service
• Now have a spare proper deep-drop fork that could be used on two other (mudguard) bikes, as well as the Dual, should the need arise
• Preliminary pre-transplant measurements suggest all components including band-on front derailleur and stem length will simply transfer as-is and allow riding position to be maintained
• Even the existing seatpost is the right size
• Rear brake cable is external (old frame’s brake line/routing was internal and poorly designed, meaning it was irritatingly stiff from new regardless of all efforts to improve it)
• BSA-threaded bottom bracket
• Replacement gear hangers have also been acquired, for a bit of future-proofing as hanger designs are constantly changing
• Cost of conversion well below the budget I'd expected to be working with

Thanks for the frame suggestions - especially to Brucey for going to the trouble of investigating and photographing his suggestion.