Minimal rear rack like this

Talk about anything.

Moderators: Bearbonesnorm, Taylor, Chew

User avatar
fatbikephil
Posts: 6511
Joined: Wed Apr 02, 2014 10:51 pm
Location: Fife
Contact:

Re: Minimal rear rack like this

Post by fatbikephil »

ScotRoutes wrote: Fri Oct 04, 2019 10:40 am While we're racking, any suggestions for a rack to fit over 4.4 - 4.8" tyres? No mounts on the frame either and it's a 12mm axle so looks like P-clips and one of those seatclamp mounts might be required.
Colin - I bought a tubus fat bike rack for the rov 150 and then never used it. It is supposed to be bolted on but if its of interest I can lend it to you.... (and sell it if it works out!)

+1 M5 bolts for racks are pish. The above rack is a substantial cromo 10mm tube thing but its held onto the bike by 4 weedy m5 screws = whats the point...... M6 barely acceptable M8 much better. Ideally? M10 hex heads as you can put a BFO (17mmAF) spanner on them and really give it some welly :mrgreen:
User avatar
sean_iow
Posts: 4269
Joined: Tue Sep 30, 2014 12:08 pm
Location: Isle of Wight

Re: Minimal rear rack like this

Post by sean_iow »

Are the M5 fixings for racks one of the only 'standards' for bikes that have been changed? Yet one of the only things that really needed changing :grin:

But stronger rack fixings don't sell bikes like a new bottom bracket standard or new handlebar clamp size.
Adventure without risk is Disneyland - Bikemonger
ScotRoutes
Posts: 8144
Joined: Mon Mar 18, 2013 9:56 am

Re: Minimal rear rack like this

Post by ScotRoutes »

htrider wrote: Fri Oct 04, 2019 9:05 pm
ScotRoutes wrote: Fri Oct 04, 2019 10:40 am While we're racking, any suggestions for a rack to fit over 4.4 - 4.8" tyres? No mounts on the frame either and it's a 12mm axle so looks like P-clips and one of those seatclamp mounts might be required.
Colin - I bought a tubus fat bike rack for the rov 150 and then never used it. It is supposed to be bolted on but if its of interest I can lend it to you.... (and sell it if it works out!)
That might be handy, even as a starter for 10. I once bought a Tubus rack for my Amazon (complete with the Tubus disk mount adapter) but it just wouldn't fit.
User avatar
Alpinum
Posts: 2603
Joined: Thu Mar 06, 2014 5:38 pm

Re: Minimal rear rack like this

Post by Alpinum »

htrider wrote: Fri Oct 04, 2019 9:05 pm +1 M5 bolts for racks are pish. The above rack is a substantial cromo 10mm tube thing but its held onto the bike by 4 weedy m5 screws = whats the point...... M6 barely acceptable M8 much better. Ideally? M10 hex heads as you can put a BFO (17mmAF) spanner on them and really give it some welly :mrgreen:
Exactly! The more, the better.
Wait...
lune ranger
Posts: 2380
Joined: Thu Dec 15, 2016 7:52 pm
Location: Peoples Republic of Devon

Re: Minimal rear rack like this

Post by lune ranger »

My Thorn eXXp uses M6 fittings on the rear rack with a matching custom rack that they rate for something like 40kg load :shock:
If you are going through hell, keep going.
WSC
slackman99
Posts: 332
Joined: Tue Jan 24, 2012 10:01 pm

Re: Minimal rear rack like this

Post by slackman99 »

An M5 4.6 grade bolt is listed at around 270kg of shear capacity in single shear. I imagine that bolt failures may involve some loosening leading to combined bending and shear on the bolt.

I suppose the weight on the rack could be multiplied when going over sharp bumps etc but for the bolt to shear with a 20kg load the rack would have to transmit over 13G into the bolt.
User avatar
fatbikephil
Posts: 6511
Joined: Wed Apr 02, 2014 10:51 pm
Location: Fife
Contact:

Re: Minimal rear rack like this

Post by fatbikephil »

ScotRoutes wrote: Fri Oct 04, 2019 9:25 pm
htrider wrote: Fri Oct 04, 2019 9:05 pm
ScotRoutes wrote: Fri Oct 04, 2019 10:40 am While we're racking, any suggestions for a rack to fit over 4.4 - 4.8" tyres? No mounts on the frame either and it's a 12mm axle so looks like P-clips and one of those seatclamp mounts might be required.
Colin - I bought a tubus fat bike rack for the rov 150 and then never used it. It is supposed to be bolted on but if its of interest I can lend it to you.... (and sell it if it works out!)
That might be handy, even as a starter for 10. I once bought a Tubus rack for my Amazon (complete with the Tubus disk mount adapter) but it just wouldn't fit.
Let me know Colin if its of interest, should be up that way at somepoint.....
User avatar
BigdummySteve
Posts: 2974
Joined: Sun Nov 20, 2016 9:16 pm
Location: Somewhere over the rainbow

Re: Minimal rear rack like this

Post by BigdummySteve »

One thing I do when fitting racks is to put the bolts through from the inside of the frame then use a nyloc nut on the protruding stud. That way in the unlikely event of it coming loose the rack strut will still sit in place, less likely to damage the frame threads as well :-bd
We’re all individuals, except me.

I woke up this morning but I’m still in the dark
middleagedmadness
Posts: 1799
Joined: Wed Nov 01, 2017 6:37 pm
Location: Tir Na Nog

Re: Minimal rear rack like this

Post by middleagedmadness »

BigdummySteve wrote: Thu Oct 10, 2019 11:36 pm One thing I do when fitting racks is to put the bolts through from the inside of the frame then use a nyloc nut on the protruding stud. That way in the unlikely event of it coming loose the rack strut will still sit in place, less likely to damage the frame threads as well :-bd
F#ck me Steve you ever worked for Hino ,that's how they build all their trucks ,bolt-flat washer-spring washer- nut-nyloc nut on every fecking bolt on the truck
User avatar
BigdummySteve
Posts: 2974
Joined: Sun Nov 20, 2016 9:16 pm
Location: Somewhere over the rainbow

Re: Minimal rear rack like this

Post by BigdummySteve »

Aye, pain in the arse but I bet things don’t fall off :-bd
We’re all individuals, except me.

I woke up this morning but I’m still in the dark
User avatar
Alpinum
Posts: 2603
Joined: Thu Mar 06, 2014 5:38 pm

Re: Minimal rear rack like this

Post by Alpinum »

When applicable I use nyloc nuts too.
For all other things macadamia.

Bolt - washer - stuff that needs to be held together - washer - nyloc nut.
Don't forget your washers!
:grin:
User avatar
JackT
Posts: 251
Joined: Tue Jan 06, 2015 3:28 pm

Re: Minimal rear rack like this

Post by JackT »

As discussed on the CTC forum ten years ago. And reaching a similar conclusion. Great minds and all that.

https://forum.cyclinguk.org/viewtopic.php?t=29456

Thread mentions Ian Hibell, who had his rear rack brazed to the frame. But then again he was doing serious load-lugging for years on end in some very hostile terrain.
hibell-bike.jpg
(91.06 KiB) Downloaded 1935 times
User avatar
Alpinum
Posts: 2603
Joined: Thu Mar 06, 2014 5:38 pm

Re: Minimal rear rack like this

Post by Alpinum »

JackT wrote: Fri Oct 11, 2019 12:30 pm As discussed on the CTC forum ten years ago. And reaching a similar conclusion. Great minds and all that.

https://forum.cyclinguk.org/viewtopic.php?t=29456

Thread mentions Ian Hibell, who had his rear rack brazed to the frame. But then again he was doing serious load-lugging for years on end in some very hostile terrain.
hibell-bike.jpg
Just as I might ask if the regular M5 mounted rack survived, the same question comes to mind with this fellow's rack.

As stated before, should the bolt fail, it's dead easy to replace it. If you make sure the interface isn't dodgy and tightened correctly, the chances are very little, that it'll snap.

Just now I'm in the process of preparing my bike to carry 15 L of water and so many days worth of food, it's basically just really stupid.
Next to bikepacking gear for a remote area, I'll be taking high altitude hiking/climbing gear with me as well.
Still, I'm going with the regular M5 and god forbid, an alu rack (just because that's what I got... and fit the bike well). The total (and worst case scenario) load without me and the bike itself should be about 55 kg. Yet the rear pannier only get's about 20 kg and the front about 10 kg. The rest is supported by structures on the frame/fork not attached to the racks.

So instead of investing in a nuke proof rear rack (mind, not detachable) or M10 bolts for it, why not just make sure your frame and fork have multiple bosses to distribute the loads more evenly, mix the rack stuff with soft bikepacking bags etc.
The bike will also be more balanced to ride. Just like trimming a boat.

Or perhaps I'll die on that trip, thanks to a failed M5 bolt... We'll see.
User avatar
JackT
Posts: 251
Joined: Tue Jan 06, 2015 3:28 pm

Re: Minimal rear rack like this

Post by JackT »

I suspect Hibell's racks were as much about improving strength, rigidity and bracing. So as to avoid the rack itself breaking and minimising the tail wagging the dog effect you can get with a heavy load on a rear rack.

Hibell was probably the most accomplished adventure cyclist of all time so knew his stuff. Worth looking up. Sadly he was killed by a truck in Greece about a decade ago.
User avatar
Bearbonesnorm
Posts: 23904
Joined: Sun Jun 05, 2011 8:53 pm
Location: my own little world

Re: Minimal rear rack like this

Post by Bearbonesnorm »

Hibell was probably the most accomplished adventure cyclist of all time so knew his stuff. Worth looking up.
Ooh yes. Certainly worth trying to track down a copy of 'Into the Remote Places'. Quite rare these days but copies do crop up.
May the bridges you burn light your way
jameso
Posts: 5036
Joined: Tue Nov 06, 2012 1:48 pm

Re: Minimal rear rack like this

Post by jameso »

M4 is not daft, the problem isn't the bolt size, it's the right torque with which it gets tightened and the contact area. Get that right and they will hold.
As you say yourself.
Putting oversized bolts in such a place is just fighting symptoms.
I wouldn't be suprised if the maths says an M5 mid-grade at the right torque would hold a 10-20kg rack w/o shear on the bolts (I haven't tried to work it out) but for a longer ride on rough roads it's not the spec I'd expect many to start out with if there wasn't an industry norm to work to already. Fighting symptoms or realistic when frames and racks flex, paint isn't a great contact surface, etc? Small gain in size/weight, 2-4x gain in lifespan from added contact area and bolt strength. I know what I'd spec on a custom bike + rack anyway. The benefit of M5s though is that we tend to have plenty of places on the frame and fork to hold spares :-bd
ScotRoutes
Posts: 8144
Joined: Mon Mar 18, 2013 9:56 am

Re: Minimal rear rack like this

Post by ScotRoutes »

htrider wrote: Thu Oct 10, 2019 10:53 pm
ScotRoutes wrote: Fri Oct 04, 2019 9:25 pm
htrider wrote: Fri Oct 04, 2019 9:05 pm
ScotRoutes wrote: Fri Oct 04, 2019 10:40 am While we're racking, any suggestions for a rack to fit over 4.4 - 4.8" tyres? No mounts on the frame either and it's a 12mm axle so looks like P-clips and one of those seatclamp mounts might be required.
Colin - I bought a tubus fat bike rack for the rov 150 and then never used it. It is supposed to be bolted on but if its of interest I can lend it to you.... (and sell it if it works out!)
That might be handy, even as a starter for 10. I once bought a Tubus rack for my Amazon (complete with the Tubus disk mount adapter) but it just wouldn't fit.
Let me know Colin if its of interest, should be up that way at somepoint.....
Well, if you're in the area and it's no problem then it's definitely worth me having a wee look at it. That would also give me the opportunity to finally met you :lol:
User avatar
Bearbonesnorm
Posts: 23904
Joined: Sun Jun 05, 2011 8:53 pm
Location: my own little world

Re: Minimal rear rack like this

Post by Bearbonesnorm »

I wouldn't be suprised if the maths says an M5 mid-grade at the right torque would hold a 10-20kg rack w/o shear on the bolts
But only with perfect hole sizes, alignment and parallel contact surfaces.
May the bridges you burn light your way
User avatar
Alpinum
Posts: 2603
Joined: Thu Mar 06, 2014 5:38 pm

Re: Minimal rear rack like this

Post by Alpinum »

JackT wrote: Fri Oct 11, 2019 7:13 pm I suspect Hibell's racks were as much about improving strength, rigidity and bracing. So as to avoid the rack itself breaking and minimising the tail wagging the dog effect you can get with a heavy load on a rear rack.
 
I see here how there are many different solutions to the actual problem; too much gear on the rack.

Of course you can load more and risk less with his approach.
But why have eg 90 % of the weight on the back and 10 % on the front when you can easily go 70:30? He could've had a dislike for the handling of a loaded front - something I don't like either.

Yet, I like to think that a more even load distribution puts less stress on the materials, making bigger bolts or welding obsolete. And after a certain weight on the back of the bike, the handling will be more balanced when distributed - no matter how much one dislikes weight up front.
A frame and down tube bag can hold a few kilograms easily too, taking more load from the rear rack.
It must be much easier today, than back in his times, to get suitable racks and bags which help to manage the loads.

This is all just pondering from my side, as I'm right in the middle of preparing my bike to carry big loads.
But what do I know, I'm not a fellow Englishman and have just cycled around the world and jokingly name cannibals as one of the risks of cycling in Africa.
User avatar
Alpinum
Posts: 2603
Joined: Thu Mar 06, 2014 5:38 pm

Re: Minimal rear rack like this

Post by Alpinum »

Bearbonesnorm wrote: Sat Oct 12, 2019 1:13 pm
I wouldn't be suprised if the maths says an M5 mid-grade at the right torque would hold a 10-20kg rack w/o shear on the bolts
But only with perfect hole sizes, alignment and parallel contact surfaces.
Exactly. And this goes for any size of bolt.
User avatar
Bearbonesnorm
Posts: 23904
Joined: Sun Jun 05, 2011 8:53 pm
Location: my own little world

Re: Minimal rear rack like this

Post by Bearbonesnorm »

Exactly. And this goes for any size of bolt.
Yes but a larger bolt will have a greater safety margin to tolerate these wonky holes, poorly machined surfaces and owners with poor mechanical skills.
May the bridges you burn light your way
User avatar
Alpinum
Posts: 2603
Joined: Thu Mar 06, 2014 5:38 pm

Re: Minimal rear rack like this

Post by Alpinum »

Bearbonesnorm wrote: Tue Oct 15, 2019 4:57 pm Yes but a larger bolt will have a greater safety margin to tolerate these wonky holes, poorly machined surfaces and owners with poor mechanical skills.
definately.

Talking about wonky things

Surly is calling all 8-pack and 24-pack owners:
https://surlybikes.com/blog/important_s ... eis%7C2019

It's that rack I had problems with putting it together. But so far so good...
Post Reply