This blog post is intended as an update to my previous post, “Puncture practice” (the sorry tale of on-road tube replacement?). My order for Schwalbe Marathon tyres for Ralph was delivered within a few days from Kobie, the Australian Brompton Distributor. While our other Bromptons have Marathon Plus tyres fitted, I decided to replace the Kojaks on Ralph with Marathons for a variety of reasons. First would be the likelihood of better puncture protection than the Kojak tyres & second, they may be easier to fit onto the Alfine 11-speed hub Sun rear rim than the M+ tyre. With Brompton recommending the M tyre in preference to the M+ & the distributor offering the M tyre for shipping, my mind was made up! I’m guessing/hoping that the on-road performance difference between M & M+ tyres won’t be noticeable. We’ve had no issues with the M+ operations & if it was any other Brompton than Ralph then I would probably stick with M+ tyres?
The removal of the front & rear tyres was only slightly more difficult with the rear Sun rim & to prove that I wasn’t imagining/exaggerating the difference between the rims, here’s a pic of the Sun rim & the old-style single-wall front rim (both fitted with thin BBB rim tape) to illustrate the profile comparison.
Fitting the M tyre to the front rim was straight-forward & by ensuring the tyre is squeezed into the valley of the rim while the remainder of the tyre is “thumbed” over the rest of the rim, the assembly was rapid. Probably a Kojak may have been easier (sorry, I’ve had no experience with fitting Brompton’s own brand tyre) but I can’t say that the M tyre was any easier than an M+ (apologies that I wasn’t attempting a back-to-back direct comparison).
As for Ralph’s rear wheel, I can only repeat a portion from the previous sentence, “I can’t say that the M tyre was any easier than an M+…” – & from my experience it’s still bloody hard! That Sun rim is terrible: the lack of valley means that the initial tyre fitment stops with about 40cm still to be pushed over the rim. From there it’s a case of rest, squeeze tyre into the well, push tyre further onto the rim & then repeat (& keep repeating). One difficulty-factor is that the tyre is new & “un-stretched”, whereas next time it should be a little easier?
Remembering my first attempt at fitting M+ onto Ralph before last year’s UK trip, I had bruised & raw thumbs. On later tyre changes, I’d installed much thinner BBB rim tape & now it’s tough for the thumbs but ok (not quick, not easy – just ok). For some time I’ve wondered how long the Sun rim will last before being worn out & have researched that Velocity Aeroheat rims are available with the 36 spoke holes required for the Alfine hub. Perhaps I should start checking whether the Velocity rim has a better profile than the Sun rim?
Another of my issues during the roadside tube replacement recently, was my CO2 cartridge tyre inflation “hiccup”. At home in the garage seemed an ideal time to get the practice I needed? I used cartridges to inflate both tyres & the results weren’t very comforting! For one I managed to get 7 bar pressure (100 psi?) but for the other, it was only 5 bar (this measured by connecting my floor pump & checking the gauge). This maximum inflation of 7 bar was what I would want in the tyre but it seems a bit “hit-&-miss”? Whereas my road bike inflations have always seemed successful, I think the greater number of spokes & the cramped space on the Brompton wheels make the exercise more fiddly? Thinking about it now, I should have first secured the Presta valve with the locking ring (or partially inflated the tyre with a hand pump?) to ensure the CO2 adapter pressure against the valve was stable – drat, more practice needed? (For the uninitiated, tyre inflation with a CO2 cartridge is almost instantaneous & if you don’t get it right – or you haven’t ensured the tyre is properly mounted, the tube isn’t pinched, etc – then your inflation result may not be “as expected”?! (Taxi?!…) Another caution to the “almost instantaneous” inflation is that the cartridge becomes freezing cold very quickly! – refer pic showing 2 cartridges: one unused, one just emptied)