MacRetro chat and rides thread

[velomaniac]

Re:

Interestingly Global Cycle Network did a test to determine which was faster ridden along a cobbled road, a road bike, a gravel bike or a 29er MTB. Now baring in mind GCN is about road bikes principally, they were shocked to discover the 29er was fastest and the road bike slowest because of tyre compliance over rough ground.
Further GCN then did a piece on a new road bike with compliant carbon rims and 28mm wide tyres than runs at low psi for a road bike that as proven to be very fast on uneven road surfaces.
Further further as Epicyclo knows, wide rims allow lower psi in tyres so possibly a 32-37 tyre width on wider rims might work quite well. Personally I favour Michelin world tour tyres which although not puncture proof have a very compliant carcass and high rubber content with a lovely round profile, very comfy at lower to mid psi.

 

[clubby]

37c.

My gravel bike has 40’s and it’s not much slower than the 28’s on my road bike.
Like Epicyclo said, the ability to run lower pressures is what helps on tracks and trails.
32 isn’t enough of a jump from what you have.

 

[Jamiedyer]

This is a very interesting and often subjective topic.
I have read a bit lately on the relative 'speed' of different volume and size tyres inn Bicycling Quarterly as well as on Jan Hienes blog. Some really interesting results though not too far from our own. Though some of the 'rolling resistance and rolling speed tests in comparison are worth taking note of. Jan did the tests himself and also had independent people test as well, as he also delved into peoples natural bias.
Personally I like my 700c x 30.5 Jack Brown mile munchers that I put on the Jack Taylor a while back. Good all round for trail work as well as road and gum wall sides. They are a large volume tyre so come up looking and feeling a bit bigger than a 30.5, high sidewall and good volume mean it has a lot of comfort on the rough stuff. For my 26 on the Trucker I run good old Marathon Duremes 26x 2.0 and such a comfortable tyre and great for all the off road and mud work a tourer has to put up with on Brian and I's rides.

Jamie

 

[epicyclo]

This was known in the early 1900s when 2" tyres were common. The exigencies of WW1 meant that they stopped producing them to conserve rubber (or something like that).

After that they were confined for supply only to the colonies where roads were rough or non existent, eg the 1938 Elswick Hopper





Until mtbs, the only wide tyre available in this country was the 26" one for the back of trade bikes and it was the very opposite of supple.

I have always been a fan of tyres with a good bit of volume. I had 38mms on the widest possible rims on my fancy lightweight in the early 1960s, much to the amusement of my contemporaries who would be using what looked like O-rings on slender rims, tyres no more than 22mm. Their airs of superiority did wane somewhat if they ever came on a road ride with me though.

My recent experience is with 2.35" Schwalbe Big Apples. They don't feel 'fast', and initial acceleration requires cranking up a fair bit of rotating mass, but I notice that even on a reasonable surface when riding with proper road bikes, I have to keep dragging my brakes on freewheeling downhills because my bike rolls faster.





At the extreme are the big slick tyres for fatbikes. I had a set of Black Floyds on mine, they didn't seem to hold me back on the road (but I'm not aero fast these days anyway).

I have done some reasonably substantial road mileage on 4" slicks and didn't notice any drag, eg





Offroad they work well on a larger variety of surfaces than I expected. I put it down to the whole of the contact area of the tyre conforming to the ground rather than relying on a tiny lug for grip. Obviously useless on real mud, but in the inbetween stage when the surface is soft but not slick, they were surprisingly good. So good that I stopped to take this pic because I thought I'd spin out - you can see where I've been, and the footprint I made to demonstrate the softness of the ground ...





My opinion is that the rolling resistance of a high volume tyre is less than that of a smaller volume tyre (provided they are of the same construction). Once you get into aero territory then aerodynamics factor in, but I see very few cyclists travelling at speeds where aero is a factor.

 

[jimo746]

Re:

Anyone know how much it'll cost me to get a water bottle rivnut removed from an aluminium frame? Bottle cage and bolt(s) still in place but just spinning in the frame. I've tried all the usual tricks to try and free the bolts off.

Or do I use this as an excuse to buy myself a Dremel style multi tool?
I've actually got a few frames to sell and I think at least 2 have this same problem too...

 

[epicyclo]

Re: Re:

Anyone know how much it'll cost me to get a water bottle rivnut removed from an aluminium frame? Bottle cage and bolt(s) still in place but just spinning in the frame. I've tried all the usual tricks to try and free the bolts off.

Or do I use this as an excuse to buy myself a Dremel style multi tool?
I've actually got a few frames to sell and I think at least 2 have this same problem too...

Have you tried spraying brake cleaner in to clean up around it, then dribble in some superglue to fix it?

 

[mr-mac]

Re:

Think pushing it at 37 and mudgaurds, think 40 will be just too far.

Will maybe take some pics and measurements tomorrow if clearance I have with brakes on.

 

[jimo746]

Re: Re:

Have you tried spraying brake cleaner in to clean up around it, then dribble in some superglue to fix it?

The old bottle cage is still stuck on there making it difficult to access, but I'll give that a go this afternoon, nothing to lose!

 

[old_coyote_pedaller]

Re:

Jim, this was years ago so memory of what I did might be faulty, I had a spinning rivnut in an old Cannondale hardtail frame.
No bottle cage just the wee bolt which was the top one in the seat-tube. I got a long thin screwdriver, I think, something with a thin narrow edge like a screwdriver anyway and pushed it down hard against the part of rivnut inside the seat-tube to jam it in the hole in tube then carefully unscrewed the bolt. Had skooshed WD40 on threads of bolt inside seat-tube and left it to soak for a while. If this hadn't worked I had thought of cutting a longish V notch with filed "grippy" bits, like a pair of pliers, in end of thin strip of steel to jam around rivnut inside frame to hold it.

You probably know this trick already, I then tightened the rivnut up using a longer wee bolt than bottle cage bolt with a nut and washer on bolt. Screwed bolt into rivnut till threads fully engaged, washer is fitted between nut on bolt and rivnut, hold bolt then tighten nut against washer/rivnut to crimp rivnut tight in frame.

 

[jimo746]

Re:

Cheers, I'll have another look at it this afternoon, it's my Cannondale SR400 road bike frame, I could really do with having 2 bottle cages on it for longer rides!
The other frames with the same problem are... Another Cannondale! :facepalm: and a Trek carbon frame that I'll be selling but it'll be easier to sell it if I fix the bottle cage Rivnuts first (unless I royally f*ck it up and damage the frame beyond repair ).