Minimal rear rack like this

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htrider
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Re: Minimal rear rack like this

Post by htrider » 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!)

+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:

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sean_iow
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Re: Minimal rear rack like this

Post by sean_iow » Fri Oct 04, 2019 9:11 pm

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.
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ScotRoutes
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Re: Minimal rear rack like this

Post by ScotRoutes » 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.

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Alpinum
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Re: Minimal rear rack like this

Post by Alpinum » Sat Oct 05, 2019 1:55 am

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
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Re: Minimal rear rack like this

Post by lune ranger » Sat Oct 05, 2019 3:46 am

My Thorn eXXp uses M6 fittings on the rear rack with a matching custom rack that they rate for something like 40kg load :shock:

slackman99
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Re: Minimal rear rack like this

Post by slackman99 » Sat Oct 05, 2019 12:11 pm

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.

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htrider
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Re: Minimal rear rack like this

Post by htrider » 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.....

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BigdummySteve
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Re: Minimal rear rack like this

Post by BigdummySteve » 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
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Re: Minimal rear rack like this

Post by middleagedmadness » Fri Oct 11, 2019 6:37 am

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

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BigdummySteve
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Re: Minimal rear rack like this

Post by BigdummySteve » Fri Oct 11, 2019 7:40 am

Aye, pain in the arse but I bet things don’t fall off :-bd
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Alpinum
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Re: Minimal rear rack like this

Post by Alpinum » Fri Oct 11, 2019 8:03 am

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:

JackT
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Re: Minimal rear rack like this

Post by JackT » 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
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Alpinum
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Re: Minimal rear rack like this

Post by Alpinum » Fri Oct 11, 2019 3:38 pm

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.

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Re: Minimal rear rack like this

Post by JackT » 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.

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.

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Re: Minimal rear rack like this

Post by Bearbonesnorm » Fri Oct 11, 2019 7:32 pm

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.
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Re: Minimal rear rack like this

Post by jameso » Fri Oct 11, 2019 9:43 pm

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

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ScotRoutes
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Re: Minimal rear rack like this

Post by ScotRoutes » Fri Oct 11, 2019 10:23 pm

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:

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Bearbonesnorm
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Re: Minimal rear rack like this

Post by Bearbonesnorm » 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.
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Alpinum
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Re: Minimal rear rack like this

Post by Alpinum » Tue Oct 15, 2019 4:43 pm

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.

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Alpinum
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Re: Minimal rear rack like this

Post by Alpinum » Tue Oct 15, 2019 4:44 pm

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.

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Bearbonesnorm
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Re: Minimal rear rack like this

Post by Bearbonesnorm » Tue Oct 15, 2019 4:57 pm

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.
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Alpinum
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Re: Minimal rear rack like this

Post by Alpinum » Thu Oct 17, 2019 6:47 pm

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...

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