Touring - What's the ideal touring chainstay length?

I've never ridden a bike with chainstays longer than 45 cm. I would love to take a Surly LHT for a spin fully loaded, everyone seems to love it's handling (46cm stays). Or better yet, I'd really like to try out the Sakkit Expedition with it's mega long 47.5 stays. But are those too long? If not, I would think they would be more common.
I've heard that the rear wheel starts to slip when climbing on dirt with the longer stays, and also be a slower climber. I really like stable handling bikes, so I'd be interested to find out at what point the negatives start to outweigh the positives.
Let's say you were ordering a custom off-road, 26" expedition touring frame. What chainstay length would you specify?

Some people like to quote an absolute size for the best chainstay length but it is relative to the rider. A petite woman riding 160mm cranks does not need the same chainstay length as a tall guy on 175mm cranks.

foot size and rack type are also varibles

There is no absolute "best" size. Most touring bikes are built with a relaxed geometry. For pure climbing you want longer stays to keep the front wheel on the ground, look at pictures of pure hill climb machines, they have extra long stays. I typically run stays in the 16.75" range or longer on a 23"+ MTB frame, with some of my 60+cm touring bikes topping out at over 17.5". I once had a Haro MTB with a "virtual" stay length of 15" or so. The short stays are usually a result of trying to get a short wheelbase for quicker handling and/or lighter weights.

Aaron:)

I've never ridden a bike with chainstays longer than 45 cm. I would love to take a Surly LHT for a spin fully loaded, everyone seems to love it's handling (46cm stays). Or better yet, I'd really like to try out the Sakkit Expedition with it's mega long 47.5 stays. But are those too long? If not, I would think they would be more common.
I've heard that the rear wheel starts to slip when climbing on dirt with the longer stays, and also be a slower climber. I really like stable handling bikes, so I'd be interested to find out at what point the negatives start to outweigh the positives.
Let's say you were ordering a custom off-road, 26" expedition touring frame. What chainstay length would you specify?

Recommend trying out some different bikes, with different lengths, including Xtracycles and the new Surly/Xtracycle setup.

By riding the shorter, longer, and extra-long stays, it will become clear to you how they affect the ride.

The extra-long stays have some very significant effects, and some people prefer them. These bikes are definitely *significantly* more stable. When going downhill on rough gravel roads, there is a night-and-day difference in stability.

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There is much better traction when you have a touring load in the rear. The tire is much less likely to slip.

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Another factor that is not often mentioned is that the front wheel receives more of your weight as chainstays get longer.

This has a much stronger effect on handling than people tend to think, especially when you go to extra-long stays.

There is increased control in many situations.

+1 to niles' explanation

I would ride 50cm if I could...

"Let's say you were ordering a custom off-road, 26" expedition touring frame. What chainstay length would you specify?"

If it was for on-road and bike specific trails, I would probably go for 60 cm. With a loaded road touring bike, I can't really power my way out of traction problems on dirt trails, riding slicks. I have to carry the mo, or forget about it. I want the longest stays I can get for the load and the ride, and don't really worry about climbing hills on roads designed for car use. Arvon Stacey makes bikes with a 50+ wheel base and his clients seem to like them. Probably not offroad enough for you though.

The guy behind Thorn runs 26" wheels on overlength stays, the stays are what look to me to be "Sakkit length", and he prefers that arrangement. He runs 2" tires so you can tell he is into the roughish stuff.

19-19.5 inches is about the max you can get with standard components, and that probably has more to do with what shows up in standard custom bikes. On deep custom bikes you aren't limited to standard parts so the sky is the limit.

The blue Arvon attached, looks to have stays in the 55 cm range.

82.7 cm (http://www.surlybikes.com/bigdummy.html)

I saw an Thorn EXP in a book, and measurement of the stays suggests they are in the 52 CM arena.