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Re: Spa Tourer as a gravel bike?

Posted: 18 Oct 2020, 12:29am
by Brucey
I have a suspicion that any front mudguard with just one stay is more dangerous than the same with two stays, because -in the event of stick coming into the mudguard- it always seems to make the chances of the mudguard crumpling (between the bottom and the fork crown) greater. This crumpling is what causes the mudguard to push upwards into the down tube and the result is always the same; you lose control of the steering and you fall off. This isn't as bad as a complete jam and going over the bars but it is still pretty bad.

A lot of recent release designs use two intimately joined pieces of plastic which are meant to slide and release when the need arises. IME joints of this type, on bicycles, tend to do one of two things, either

a) rattle themselves loose or
b) get a lot of grime in the interface and start to bind.

Either will affect the release of course.

The original secu-clip wasn't perfect by any means but it had an interface where dirt would tend to be pushed out of the way during a release (rather than cause a complete jam) and in addition the stays can always be reshaped so as to compensate for wear etc and keep the release force within sensible limits.

Many newer designs seem to lack these rather basic features; they may look good on the drawing board, work well in lab tests, and yet be poor in the real world.

BTW 'gravel bikes' are basically lightly warmed over touring bikes. Of course you can ride offroad on touring bikes!

cheer

Re: Spa Tourer as a gravel bike?

Posted: 18 Oct 2020, 4:55am
by pwa
My own Spa Tourer is the titanium one (with the same steel forks) so it might be slightly different, but it runs 35mm tyres with something like 10mm clearance with guards, so taking the guards off would make room for tyres a bit bigger than that. I reckon it would give a bike that, in experienced hands, would handle nicely on forest tracks. So yes, you would have something that could take what used to be called "Roughstuff". The only downside compared to a Gravel Bike is the reduced bite of the brakes in extreme conditions such as very steep off-road descents (but do you do extreme conditions?) and rim wear. The rim wear issue would only be a big factor if you made a habit off off-roading in the wet. Other than that, for forest trails and towpaths the Spa would be a nice option. It seems like a good use of the frameset.

Re: Spa Tourer as a gravel bike?

Posted: 18 Oct 2020, 6:03pm
by 531colin
slowster wrote:... That leaves the question what the maximum tyre size is in the Tourer fork with full size V brakes or cantilevers......


Not to mention the question of tyre clearance at the chainstays.
What gap have you got between your 36.5mm tyre and the chainstay?

Re: Spa Tourer as a gravel bike?

Posted: 18 Oct 2020, 6:10pm
by 531colin
pwa wrote:My own Spa Tourer is the titanium one (with the same steel forks) so it might be slightly different, but it runs 35mm tyres with something like 10mm clearance with guards, so taking the guards off would make room for tyres a bit bigger than that. I reckon it would give a bike that, in experienced hands, would handle nicely on forest tracks. So yes, you would have something that could take what used to be called "Roughstuff". The only downside compared to a Gravel Bike is the reduced bite of the brakes in extreme conditions such as very steep off-road descents (but do you do extreme conditions?) and rim wear. The rim wear issue would only be a big factor if you made a habit off off-roading in the wet. Other than that, for forest trails and towpaths the Spa would be a nice option. It seems like a good use of the frameset.


Same question. Whats the gap between tyre and chainstay?
(in my defence, it must be 10 years since I designed it, there have been 2 frame factories for the Titanium in that time, probably 3 factories for steel frames, and maybe 4 for steel forks.
This fork crown is different to the photo I posted previously, its the same argument from a previous occasion (2012 photo....first lot was 2014)
Image002 by 531colin, on Flickr

Re: Spa Tourer as a gravel bike?

Posted: 18 Oct 2020, 6:30pm
by pwa
531colin wrote:
pwa wrote:My own Spa Tourer is the titanium one (with the same steel forks) so it might be slightly different, but it runs 35mm tyres with something like 10mm clearance with guards, so taking the guards off would make room for tyres a bit bigger than that. I reckon it would give a bike that, in experienced hands, would handle nicely on forest tracks. So yes, you would have something that could take what used to be called "Roughstuff". The only downside compared to a Gravel Bike is the reduced bite of the brakes in extreme conditions such as very steep off-road descents (but do you do extreme conditions?) and rim wear. The rim wear issue would only be a big factor if you made a habit off off-roading in the wet. Other than that, for forest trails and towpaths the Spa would be a nice option. It seems like a good use of the frameset.


Same question. Whats the gap between tyre and chainstay?
(in my defence, it must be 10 years since I designed it, there have been 2 frame factories for the Titanium in that time, probably 3 factories for steel frames, and maybe 4 for steel forks.
This fork crown is different to the photo I posted previously, its the same argument from a previous occasion (2012 photo....first lot was 2014)
Image002 by 531colin, on Flickr

Just had a quick look with no tape measure to hand, and at the chainstay I reckon there is 10mm gap with Marathon Supreme 35mm on Grizzly rim. At the fork there is a bigger gap to the fork blades. On forest tracks I'd not want to lose much of the clearance around the front wheel but I might risk it at the back.

Re: Spa Tourer as a gravel bike?

Posted: 18 Oct 2020, 8:45pm
by slowster
531colin wrote:What gap have you got between your 36.5mm tyre and the chainstay?

I did measure it yesterday but didn't mention it because like pwa I have the Ti Touring rather than the steel Tourer. For what it's worth the clearance is 10mm on the drive side, but I cannot quite slide my 10mm allen key in the gap on the non-drive side, so that is around 9mm.

Anyway I guess that for the OP's purpose what matters is that he can probably easily fit 40mm tyres and probably nearer 45mm. With regards to the original question, if anything I would prefer the handling of the Tourer off road to a typical gravel bike, because I think the longer wheelbase and chainstays give a more relaxed and stable ride.

Re: Spa Tourer as a gravel bike?

Posted: 18 Oct 2020, 9:13pm
by iandriver
Personally, I'd forget the gravel bike thing. They are changing every year, ever bigger tyres etc.

I think your problem is, you have two very similar frames and want two distinct bikes.

The answer, to me, is in the build. Build it lighter, no racks etc. Tyres more suited to off road. Or even a much lighter fork. All depends how far you want to go.

Personally I'd just build it up, fit some 38c off road tyres like Smart Sam's, carridice saddle bag or similar and just enjoy it.

Re: Spa Tourer as a gravel bike?

Posted: 19 Oct 2020, 7:02pm
by 531colin
slowster wrote:.........Anyway I guess that for the OP's purpose what matters is that he can probably easily fit 40mm tyres and probably nearer 45mm......


The bike fits 35mm tyres with 10mm under the guard.....so fitting 40mm tyres is hardly newsworthy.
2 replies suggest the chainstay clearance is about 55mm. That will be about right; the widest fork crown Spa regularly use gives 60mm between the fork legs (at the crown) and the chainstay clearance is significantly less than this. (Its a 10 year old design....the Bob Jackson Tourer I was riding at the time maxed out at 28mm tyres with less than 10mm under the guards.)
If you fit a 45mm tyre in a 55mm gap, you will need to be pretty handy with a spoke key if you break a spoke or your wheel gets more than fractionally bent while you are out. Why risk it? Is there a real measurable difference between riding 40 and 45mm tyres?
For more recent designs with manipulated chainstays I have made the chainstay clearance the same as the fork, 60mm. ...I suppose somebody will want to fit 2 inch tyres!
How much of this is fashion? I have done some pretty nice tracks on 35mm Marathons....this is approaching Skiddaw hostel from the north west.

Image005 by 531colin, on Flickr

Re: Spa Tourer as a gravel bike?

Posted: 19 Oct 2020, 9:16pm
by slowster
531colin wrote:If you fit a 45mm tyre in a 55mm gap, you will need to be pretty handy with a spoke key if you break a spoke or your wheel gets more than fractionally bent while you are out. Why risk it? Is there a real measurable difference between riding 40 and 45mm tyres?

It may not be a question of choosing the 40mm or 45mm version of a tyre, but rather that someone might want to fit a tyre that is only available as a 45mm, or at least is only available at a bargain price in the 45mm size. There seem to be quite a few tyres marketed for the gravel bike market at around that size. As for the risk I would be happy to risk it on a local ride but not on a tour, but the OP might take a different view.

531colin wrote:How much of this is fashion?

I don't disagree, but the OP asked specifically about using a Spa Tourer frameset as a gravel bike, rather than whether the frame is suited for any particular types of off road terrain, which is implicitly asking what are the differences between a Spa Tourer and a typical gravel bike, and what is the significance of them? Gravel bike fashion seems to be >40mm tyres, shorter chainstays than traditional touring geometry and (I think) a bit more trail than a Spa Tourer (I might well be wrong about that). What the effect of all that is on the handling compared with a Spa Tourer is something I am still trying to gauge myself.

531colin wrote:I have done some pretty nice tracks on 35mm Marathons....this is approaching Skiddaw hostel from the north west.

That looks absolutely lovely. Remind me again, what tyre width are you running now on your Roughstuff? :wink:

Re: Spa Tourer as a gravel bike?

Posted: 19 Oct 2020, 9:22pm
by Jdsk
Great photo.

We once watched a peregrine knocking down pigeons from there. At the same time as the BBMF Lancaster came over very low. And we only had one pair of binoculars...

Jonathan

Re: Spa Tourer as a gravel bike?

Posted: 20 Oct 2020, 9:11am
by 531colin
Jdsk wrote:Great photo.

We once watched a peregrine knocking down pigeons from there. At the same time as the BBMF Lancaster came over very low. And we only had one pair of binoculars...

Jonathan


these are the days we remember!

Re: Spa Tourer as a gravel bike?

Posted: 20 Oct 2020, 9:18am
by 531colin
slowster wrote:......... Remind me again, what tyre width are you running now on your Roughstuff? :wink:


I think they are nominally 40. I've got a couple of busy days and its absolutely blathered in mud, so I'll clean it up, measure, and take a photo when I get a chance.
Tyres as here..https://forum.cyclinguk.org/viewtopic.php?f=1&t=140851&p=1528133&hilit=schwalbe#p1528133
Except as it says there the tread pattern seems to be different now to when I bought them; I think I paid 10 either euro or pounds.

Re: Spa Tourer as a gravel bike?

Posted: 20 Oct 2020, 9:32am
by pwa
One thing that we all know is that an adaptable frameset like a Spa Tourer can be asked to do a wide range of things it might not be the best at, and do them in a very satisfactory way. It was not designed as a dedicated off-roader and will certainly need more careful handling on tracks where very wide tyres would be better. But does that matter? I did about seven miles of a rough gravel track, in the summer, on my 35mm Supremes, sometimes riding over loose 30mm chippings, and both the tyres and the bike behaved well. If I rode that track every day I would be on a different bike with wider tyres, but I don't, so I was happy to make do with a bike and tyres that are at their best on less bumpy stuff. You have to consider what the "normal" surface conditions will be for the bike and how far from that "normal" you expect your tyres and bike to be able to go. 35mm touring tyres will go over compacted stone dust paths much as they would over tarmac, and as the roughness of the path increases you can continue to ride but your comfort will decrease, the need for concentration will increase, and your speed will drop.

Re: Spa Tourer as a gravel bike?

Posted: 20 Oct 2020, 9:41am
by ANTONISH
In 1960 I was in Ireland - I had my road bike with sprints and tubulars.
A local cyclist invited me on a club run in the Wicklow hills.
We were riding up a climb when the leader turned onto a track which descended to a bog.
We walked through that for a while and came to a river - forded the river carrying our bikes and continued through the bog and eventually reached a tarmac road.
We used to go off road on any bike available - now there seems to be a range of hardly different machines designed for different surfaces.
I don't know what the original members of the Roughstuff fellowship would have thought of it.

Re: Spa Tourer as a gravel bike?

Posted: 20 Oct 2020, 1:28pm
by Bmblbzzz
I imagine many of them would be delighted to have a gravel bike or hardtail mountain bike as a versatile, on and off road machine. This is the point of gravel bikes, surely - the spiritual successor to the roughstuffers' bike.