My miniture Schnauzer is now about 18 months old and in the last couple of weeks she has developed a brown strip of fur down her back.  She is a pepper and salt colour and very soft whereas this brown fur is quite course, simiular to a border terrier fur.

Anyone got any ideas why this should suddenly happen.  She looks a bit weird!!??!!??

It may be the proper coat coming through?  Mini Schnauzers are not supposed to have a soft coat but a harsh wire coat - can't imagine why it's brown tho

Have you contacted the breeder?  surely they would be best able to answer your question ;)

I have seen this quite often.  If she was stripped all over it would probably balance out.

Sounds as though the soft puppy coat needs to come out.  Do have her hand stripped not clipped and see what comes through. :)

My min schnauzer has a very light brown coat down her back and because her coat is kept very short you hardley notice it. She also has the same colour under her muzzle. must admit  i've never really thought about it before and pressumed it was meant to be like that.
My shnauzer is 4yrs old and this brown colour has been more noticeable as she's got older.
I've got her coat really short at the moment but have left it to grow quite long before and it is very thick and wavy but when short it looks smooth and totally different. 

We had a 1 year old min schnauzer in the other day and I had to laugh at the owners instructions-please leave him quite fluffy on his back-if he's taken too short it his coat goes too wiry! Managed to talk them into having him taken shorter luckily.