Tubus Tara different?

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slowster
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Re: Tubus Tara different?

Post by slowster »

gregoryoftours wrote: 2 Feb 2023, 10:12pm Maybe they've re-jigged the design to better fit a more modern style of fork. Many of these have blades that stay wide further up the fork to give greater clearance at the crown to take wider tyres. I mean this kind of thing...
The diagram of the fork in the installation instructions is indeed a fork just like that:
fork.jpg
rogerzilla
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Re: Tubus Tara different?

Post by rogerzilla »

My Tara can't be adjusted to sit level on a Surly LHT fork. The slot just isn't long enough. I don't think it's a good design.
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531colin
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Re: Tubus Tara different?

Post by 531colin »

rogerzilla wrote: 3 Feb 2023, 7:55am My Tara can't be adjusted to sit level on a Surly LHT fork. The slot just isn't long enough. I don't think it's a good design.
Or Surly want you to buy their own carrier?
slowster
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Re: Tubus Tara different?

Post by slowster »

gregoryoftours wrote: 31 Jan 2023, 8:36pm I am satisfied with the strength and support as I have it fitted.

Here are some photos of the bike on tour
As a matter of interest, how much weight do you carry in the front panniers?

I do like the look of your bike. Am I correct in thinking that you have changed the fork for one with a shorter axle to crown measurement? Compared with what I presume was the fork that came fitted, as shown in the photograph below which I found when searching for information about the Gary Fisher Aquila, your fork looks maybe 30mm shorter. Was the effect of that on the head angle and trail noticeable?

Image
rogerzilla
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Re: Tubus Tara different?

Post by rogerzilla »

531colin wrote: 3 Feb 2023, 9:09am
rogerzilla wrote: 3 Feb 2023, 7:55am My Tara can't be adjusted to sit level on a Surly LHT fork. The slot just isn't long enough. I don't think it's a good design.
Or Surly want you to buy their own carrier?
I think the cause is that Surly provide two eyes at the fork end but, due to the stupid sculpted casting design, only one is usable. The other one may give the correct geometry but you'd need some kind of standoff spacers, which would weaken the bolted joint.
Woodtourer
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Re: Tubus Tara different?

Post by Woodtourer »

I have the Tara on both of our touring bikes Mine is a LHT and my wife's was one but is now a Dutch frame. I have used spacers at both mid fork and dropout. Tours across the United States, Canada and multi month European tours. Never had an issue with bolts bending or breaking. Also I work in a bike shop and overhaul the bikes before and after our tours so I pay particular attention to all the bolts.
pwa
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Re: Tubus Tara different?

Post by pwa »

Woodtourer wrote: 4 Feb 2023, 1:17am I have the Tara on both of our touring bikes Mine is a LHT and my wife's was one but is now a Dutch frame. I have used spacers at both mid fork and dropout. Tours across the United States, Canada and multi month European tours. Never had an issue with bolts bending or breaking. Also I work in a bike shop and overhaul the bikes before and after our tours so I pay particular attention to all the bolts.
And if in doubt, it is only a very small and inexpensive job to replace potentially over-stressed bolts once in a while, just to be on the safe side.

But my old stainless Tara fits more or less flush on my Spa Tourer forks. I stick washers between surfaces just to reduce paint damage. The rack, when not on the bike, measures 130mm at the mid fork mounts, and 150mm at the drop-out mounts. There is quite a lot of easy flex in the rack when not on the bike, so the 150mm at the base easily springs in to much less than that, and the 130mm at the mid-fork will go to 120mm without much effort. I haven't got the rack on the Spa forks at the moment, but I think it takes no more than a very few washers to get a perfect fit with no paint being rubbed. The fork was obviously designed to take that sort of rack, or vice versa. Colin does a nice job with his tape measure.

The measurements on my (older) rack are different to those in the OP. Perhaps it would be best to source a rack from a supplier you can speak to, who would be willing to get a tape measure out and examine the rack for you before you agree to buying. Spa have them, and I'd be on the phone to them if I needed that sort of advice. If you explain that you have had a duff out-of-spec example before, they might take the trouble to get one out and check it for you.
slowster
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Re: Tubus Tara different?

Post by slowster »

PT1029 wrote: 2 Feb 2023, 9:18pm I don't think suggestions of the horizontal bar mounting at an angle in the U bar due to the (radially) loose fit of the bolts through the U bar works. Although there is slop/wiggle room for the bolt, the rod will tighten flat to the mounting surface of teh U bar, which places them wide at the fork again. It would take curved a la V brake washers to permit this. It did cross my mind to try, but I though I'd aim to send it back in the hope it's replacement was better.
I think that gregoryoftours is right, and the spacing is intended to be that wide to suit slightly wider forks.

An alternative to curved washers might be to file the outside edge of the cylindrical boss in the u bar to alter the angle of contact of the horizontal strut, and thus reduce the spacing at the mid-fork mount.
gregoryoftours
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Re: Tubus Tara different?

Post by gregoryoftours »

slowster wrote: 3 Feb 2023, 3:24pm As a matter of interest, how much weight do you carry in the front panniers?

I do like the look of your bike. Am I correct in thinking that you have changed the fork for one with a shorter axle to crown measurement? Compared with what I presume was the fork that came fitted, as shown in the photograph below which I found when searching for information about the Gary Fisher Aquila, your fork looks maybe 30mm shorter. Was the effect of that on the head angle and trail noticeable?

Image
Wow, my bike is small but that one looks minute! Yes the axle to crown spec of the Surly LHT fork that I have on it now is 376mm. The original I measure as 410mm or maybe just a touch less, so quite a big difference. I didn't notice a huge change in how the bike handles (in actual fact I didn't notice any change at all, although I wasn't really looking out for it). It is very planted, especially loaded up, and not a hint of wobble. I guess the low center of gravity helps with that. I really love how it rides, both loaded and unloaded. Unloaded it's nimble but not twitchy.

I try not to put too much weight in the front panniers but not too little either, generally maybe 3 or 4 kilos in each side.
PT1029
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Re: Tubus Tara different?

Post by PT1029 »

Before I phone Spa (from where I got the rack), I thought I'd do a few more/check measurements.
U bar assembled with pannier hook bars so the are snug (no side play/flex): -
Pannier hook bars do not assemble parallel, inside widths are (U bar unsprung): -
At U bar, pannier hook rails are 140mm wide, at mid fork mount, 163mm wide, so 23mm taper.

U bar unsprung, dropout spacing (inside of mounting bracket) on U bar is 135mm

I have no spare forks floating about, but measuring my tourer, outside dropout width is near enough 120mm.
Allowing for some spacing (as is otten needed at the dropout) I sprung the U bar in and then measured the mid fork mount point width (inside measurement).

U bar sprung in to 120mm outside dropout width, rack mid fork mount point width 145mm. Actual fork width 120mm, so 12.5mm spacers per side
U bar sprung in to 125mm outside dropout width, rack mid fork mount point width 154mm. Actual fork width 120mm, so 17mm spacers per side
NB. I think Tubus blurb said recc max 8mm spacers.
NB. Using 17mm spacers each side is too much in my view, in terms of bolt stress.
NB. Spinging the U bar into 120/125mm dropout width didn't need that much force, and its a chunky bar, so OK to do in my book.

Tubus rec dropout width of 124 - 134mm, so the 2nd line (in bold) applies.
Tubus rec mid fork width is 130 - 140mm, so 2nd line in bold is 14mm over the upper limit for mid fork width.

If the pannier hook rails were parallel, the mid ford mount width would be 23mm less (no taper) than 154mm, so would be 131mm wide, which is within Tubus spec. of 130 - 140mm width.

Tubus may have tweeked the design for wider forks but not updated the paperwork?
Or maybe the U bar pannier hook rail mounts are incorrectly aligned so the rails are not parallel when they should be(?), but taper outwards as they go towards the fork blades?
PT1029
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Re: Tubus Tara different?

Post by PT1029 »

I spoke to Spa (Bob) who said sometimes they have to "spring things a little" in their workshop, depending on the set up, using a feel of what feels ok and what feels would be too much. He thought cold setting a bit could be a way forward, and better than the "fit stressed" solution that Tubus suggested to me.

I'll see what random bits of steel I have to use as a curved former when I next try to fit it. Obviously I'll keep any bend/curve off any weld.
colin54
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Re: Tubus Tara different?

Post by colin54 »

PT1029 wrote: 6 Feb 2023, 11:37am I spoke to Spa (Bob) who said sometimes they have to "spring things a little" in their workshop, depending on the set up, using a feel of what feels ok and what feels would be too much. He thought cold setting a bit could be a way forward, and better than the "fit stressed" solution that Tubus suggested to me.

I'll see what random bits of steel I have to use as a curved former when I next try to fit it. Obviously I'll keep any bend/curve off any weld.
I tried to cold set a rear Tubus rack rather than use spacers on the mounting bolts, big mistake, it cracked at a weld and carried on into the tube.
Different set up on a front rack of course, but it's mighty thin tube all the same - less than 1mm. I believe stainless steel is a bit less ductile than Cr-Mo steel - more difficult to bend (more likely to crack ?) .
P1170312.JPG
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thirdcrank
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Re: Tubus Tara different?

Post by thirdcrank »

Total numptie here.

I notice that quite early on you mentioned using a pipe bender but since then seem .. er .. bent on improvising one.

Some years ago I bought a Tubus Fly (stainless steel) with a three-point fixing. This included a rod - ie not a tube - running from the back brake bridge to the rack which needed bending to fit. Memory a bit vague now because the bike had bosses for four-point fitting so I can't remember why I didn't buy the appropriate extra bits to do that, possibly pure meanness. Anyway, I consulted one of my sons who is a mechanical fitter but who was working abroad at the time. He explained in detail how to use a pipe bender - most of his tools were stored in my garage - and bingo! Perfect.
slowster
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Re: Tubus Tara different?

Post by slowster »

PT1029 wrote: 6 Feb 2023, 11:37am I spoke to Spa (Bob) who said sometimes they have to "spring things a little" in their workshop, depending on the set up
For the record/your further information, the outside to outside measurement of the lower (wider) of the two mid-fork mounts of the Spa steel touring fork is ~110mm. On the Wayfarer fork it is ~125mm (due to the boss being through the fork blades, the blades being much larger diameter, and the fork crown also being wider). I would guess that Spa must have fitted a lot of Tara racks to their steel touring fork over the last decade.

Regarding your comment "Obviously I'll keep any bend/curve off any weld", I would interested to learn how you get on. I would imagine that the bend should ideally be close to the eyelet that fastens to the U bar, in order that the rest of the horizontal strut that will be between the two pannier hooks remains completely straight. However, I presume that the closer the bend is to the eyelet, potentially the more care is needed to avoid putting bending force through the eyelet weld when doing the cold set.
colin54 wrote: 6 Feb 2023, 12:28pm I tried to cold set a rear Tubus rack rather than use spacers on the mounting bolts, big mistake, it cracked at a weld and carried on into the tube.
I did the opposite and cold set a Tubus cro-mo rack to fit a wider spacing at the drop out, and although I was worried about something similar happening it was quite straightforward. I've had heavy full pannier loads on the rack and there is no sign of cracking (yet).

However, I may just have been lucky, because I all I did was put the rack on the floor on its side, put one foot on the bottom of the rack and pulled the other side up a couple of times until it measured the required new width. In other words, I did not 'isolate' or protect the welds from the force I applied, and I would try to do that if I ever repeated the exercise. I suspect that is easier said than done, because on many Tubus rear racks one of the uprights is triangulated/canted inwards.
pwa
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Re: Tubus Tara different?

Post by pwa »

Surely the way to narrow a Tara would be to simply sit on the main (forward) U bend, to put it crudely. No welds anywhere near there, and the amount of extra bend would be quite small. The question is, how to isolate the bending to the U itself.
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