Hey STW! Faced with a big dilemma hear, was hoping someone with more knowledge and experience than myself could chip in? 😀 Basically my front rim is trashed (Kris Holm 47mm), so upgrade time! I’m torn between whether to get 30mm or 50mm rims. I have a 35 (actually 30) Vapour at the front but it gives a much much rounder profile. My LBS was explaining to me that because the rim is narrow and the Knard is so wide you get a much rounder profile than if you were to use a narrow tyre, leading to less contact patch wit the wider tyre which is kind of ironic really. But I’ve tried the ECR with normal tyres and the BB is very low, I’ve heard I really shouldn’t ride it with normal 29er tyres? What would you guys do? Go with Scrapers or Mulefuts or just build another rear Vapour wheel?
I’m really confused! Would really appreciate some input! I’m using it mainly for commuting if I’m honest right now..

Here’s some pics for further reference! (:

And just one of the whole bike if you were curious 😉

Bump, anyone?

You’d be fine running 29er tyres. The BB will be low, but not ridiculously so. Personally I’d match the rim to the front, but that’s only because I’m a bit of a tart and it would annoy me. If you’re using mismatching rims the wider should go on the front, more advantages (air volume) on the front.

Thanks for the input, think I should try it again! And I was going to get either another new set (Scrapers) or just get another Vapour. Though having non 29er plus tyres kinda defeats the point of the ECR and they are so much fun! Still confused haha

Personally I would go wider than narrower given the intended purpose of the bike.

Something like a Dually might be a good option as at 45mm it will plump up a non plus sized tyre nicely but still offer more than enough support for a plus sized tyre.

My Rabbit Hole rims and Hugo rims dramatically change the profile of a non plus tyre – IMHO not in a good way but my Dually works well with even a 2.2” tyre – I appreciate tyre casings and profiles vary hugely.

So in a rather long winded way …. go wider!

BB drop on the ECR is 80mm, which is a lot, but rideability totally depends on its intended use.

The LHT has a BB drop of 78mm, and with 35mm tyres the pedals are close to the ground but its perfectly fine for rough track, just not ones with ruts on. The Ogre has 68mm drop and people have no problem with those. An ECR with the same tyres as an Ogre, 12mm closer to the ground, its not a lot but you will notice it on occasion.

Ive heard of a few people going narrower to reduce the width of the contact patch to reduce the amount of knobs on the ground for a bit more speed. This may impact grip slightly on offcamber offroad and may induce a bit of roll, but if you are running knards then this is probably not really your focus.

Also, this statement…

My LBS was explaining to me that because the rim is narrow and the Knard is so wide you get a much rounder profile than if you were to use a narrow tyre, leading to less contact patch wit the wider tyre which is kind of ironic really

is bollocks. Not only for the fact a the tyre is so much larger that its physically impossible for a smaller tyre to form a flatter tangent to the ground width wise, not to mention the fact the length of the contact patch is what gives you most of the grip. Of course this is only possible because you will be running less pressure in the bigger tyre, so the contact patch will be bigger regardless of its shape.

Thanks for the advice, letmetalktomark, is there really that much difference between 50mm and 40mm? I really like the Scrapers and the Velocities are much harder to get so would probably go with those!

@Stato, the thing is the 80mm drop is with the 3″ tyres, without it would be about an inch lower right?
and sorry but I don’t agree, I think it makes sense. note I’m running them on relatively high pressures. The smaller rim causes the tyre to become so much more rounded and twitchy as well, which I’m pretty sure is due to less contact with the ground. I did a rough paint sketch but this is how I see it, with the second one being a normal sized rim, obviously they’re not that straight but you get the point: http://imgur.com/i6O2n7d

I tried my Knards on Flow rims which some have said works fine. I even know of a chap running them on Crests locally!

To negate the roll a much higher psi is needed and with their tread profile, I found, they need the cush to grip.

Scrapers are 45mm too so I would say you would be fine with them and a variety of tyres.

Its 80mm drop is drop from the centreline between the axles, it does not change with tyre size, BB height is a result of bb drop and tyre size.

The LHT, ECR and Ogre all have the same rim size so the bb drop can be compared. Someone (maybe surly?) did a blog post a while back about running different size tyre on an ECR, it said (IIRC) that the ECR could run with 35mm touring tyres as it would be the same BB height as the LHT, running standard mtb tyres would be lower than an OGRE by a little bit.

Your image gets the point across but you cant make a normal tyre square, the carcass will still try and form a circle (with a flat edge across the rim) within the boundaries of its design. Widening the rim increases the effective diameter of this circle but it would only provide a bigger contact width if the rim was as wide as the tyre, which a 35mm rim is not (for a 2″ tyre). And if you are running a knard firm, you would be running 2″ tyre would be firmer to be a fair comparison.

@Letmetalktomark you’ve made me even more confused now! the Vapours will cost me another £50 and the scrapers will cost £230, I just wonder if it’s worth it

@STATO ohhh! My bad, and wow that’s good news then I guess! Thank you for explaining it to me (: I thought the BB drop was one of the biggest issues of the ECR and just accepted it couldn’t run standard tyres without ever really trying them properly, stupid of me, I know! Guess I should give normal tyres another go then! Ad that makes sense, so the contact patch of the tyre is really defined by the rim width?

http://www.wiggle.co.uk/velocity-rims-dually-mtb-rim/ £208 😉

Vapour rims are only 26mm aren’t they?

My bad, and wow that’s good news then I guess! Thank you for explaining it to me (: I thought the BB drop was one of the biggest issues of the ECR and just accepted it couldn’t run standard tyres without ever really trying them properly

Don’t get me worng, it will be low. Im just pointing options out. As with rim width the choice to accept a low BB depends on what you intend to ride it on.

My Cross bike (surly) has a bb drop of 66mm and runs 685mm diameter wheels, so bb height is 276.5mm
The ogre has 68mm drop and runs 737mm wheels. BB height is 300.5
So an ECR with 80mm drop running 737mm wheels has BB height of 288.5mm

So still has a higher bb from the ground than the crosscheck and that’s been fine for most offroad stuff. So just an example, but as said it depends how you intend to use it.

Also worth noting, HALO now do a vapour 50 as well as the 35 and original 26mm.

@Letmetalktomark, I have the Vapour 35s which are 35 external (which is pretty much irrelevant right?) and 30mm internal! And hehe the Dually’s look good but Scrapers are only £5 more each…this is getting annoying now haha

@STATO it actually doesn’t seem so bad though when you put it that way! And I’m still confused as heck. Think I might just get another Vapour for £50 then upgrade later if I see the need? (:

edit: oh my god I DID NOT SEE THOSE
edit 2: it turns out they’re not availible til march the 31st!
edit 3 : they’re actually £5 cheaper than my 35s weirdly enough but they weigh over 200g more

Having used Duallys myself, I would say they fit the bill perfectly.

Nice support/profile @ 3in, possibly to run 2.2-2.4 tyres in a pinch.